diff --git a/serpentTools/parsers/results.py b/serpentTools/parsers/results.py
index d46a7fd..095cb6c 100644
--- a/serpentTools/parsers/results.py
+++ b/serpentTools/parsers/results.py
@@ -183,9 +183,10 @@ class ResultsReader(XSReader):
         """Process universes' data"""
         brState = self._getBUstate()  # obtain the branching tuple
         values = str2vec(varVals)  # convert the string to float numbers
-        if not self.universes or brState not in self.universes.keys():
+        if brState not in self.universes:
             self.universes[brState] = \
                 HomogUniv(brState[0], brState[1], brState[2], brState[3])
+        if varNameSer == self._keysVersion['univ']:
             return
         if varNameSer not in self._keysVersion['varsUnc']:
             vals, uncs = splitValsUncs(values)

[BUG] ResultsReader fails when only group constants are requested
## Summary of issue
When restricting the scope of the variables extracted from the results file to only group constants, the reader fails. 

It is also worth noting that, when non-group constant data are requested as well, 'ABS_KEFF' and 'INF_FLX', for example, the reader will not fail, but the universes produced will not have group constant data

## Code for reproducing the issue
```
import serpentTools
serpentTools.settings.rc['xs.variableExtras'] = ['INF_FLX', ] 
serpentTools.readDataFile('pwr_res.m')
```
Alternative case
```
import serpentTools
serpentTools.settings.rc['xs.variableExtras'] = ['INF_FLX', 'ABS_KEFF'] 
r = serpentTools.readDataFile('pwr_res.m')
u = r.getUniv('0', index=1)
u.infExp
# returns {}
```
## Actual outcome including console output and error traceback if applicable
```
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/data/__init__.py", line 70, in readDataFile
    return read(filePath, **kwargs)
  File "/home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/parsers/__init__.py", line 149, in read
    returnedFromLoader.read()
  File "/home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/parsers/base.py", line 49, in read
    self._postcheck()
  File "/home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/parsers/results.py", line 345, in _postcheck
    self._inspectData()
  File "/home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/parsers/results.py", line 342, in _inspectData
    .format(self.filePath))
serpentTools.messages.SerpentToolsException: metadata, resdata and universes are all empty from /home/ajohnson400/.local/lib/python3.6/site-packages/serpentTools-0.5.4-py3.6.egg/serpentTools/data/pwr_res.m and <results.expectGcu> is True
```
## Expected outcome
The parser should respect the settings passed, and properly store all the requested data on the homogenized universes
## Versions

* Version  from ``serpentTools.__version__`` `0.5.4`

* Python version - ``python --version`` `3.6`
diff --git a/serpentTools/tests/test_ResultsReader.py b/serpentTools/tests/test_ResultsReader.py
index 03e9d28..1384c4d 100644
--- a/serpentTools/tests/test_ResultsReader.py
+++ b/serpentTools/tests/test_ResultsReader.py
@@ -8,7 +8,7 @@ from numpy.testing import assert_equal
 from six import iteritems
 
 from serpentTools.settings import rc
-from serpentTools.data import getFile
+from serpentTools.data import getFile, readDataFile
 from serpentTools.parsers import ResultsReader
 from serpentTools.messages import SerpentToolsException
 
@@ -597,6 +597,40 @@ class TestResultsNoBurnNoGcu(TestFilterResultsNoBurnup):
             self.reader.read()
 
 
+class RestrictedResultsReader(unittest.TestCase):
+    """Class that restricts the variables read from the results file"""
+
+    expectedInfFlux_bu0 = TestReadAllResults.expectedInfVals
+    expectedAbsKeff = TestReadAllResults.expectedKeff
+    dataFile = "pwr_res.m"
+
+    def _testUnivFlux(self, reader):
+        univ = reader.getUniv('0', index=1)
+        assert_equal(self.expectedInfFlux_bu0, univ.get("infFlx"))
+
+    def test_justFlux(self):
+        """Restrict the variables to gcu inf flux and verify their values"""
+        with rc:
+            rc['xs.variableExtras'] = ["INF_FLX", ]
+            r = readDataFile(self.dataFile)
+        self._testUnivFlux(r)
+
+    def test_xsGroups(self):
+        """Restrict the variables groups to gc-meta to obtain flux and test."""
+        with rc:
+            rc['xs.variableGroups'] = ['gc-meta', ]
+            r = readDataFile(self.dataFile)
+        self._testUnivFlux(r)
+
+    def test_fluxAndKeff(self):
+        """Restrict to two unique parameters and verify their contents."""
+        with rc:
+            rc['xs.variableExtras'] = ['ABS_KEFF', 'INF_FLX']
+            r = readDataFile(self.dataFile)
+        self._testUnivFlux(r)
+        assert_equal(self.expectedAbsKeff, r.resdata['absKeff'])
+
+
 del TesterCommonResultsReader
 
 if __name__ == '__main__':

pip install -e .
parse_log_pytest
pytest
pytest flake8>=3.1.0 pandas>=0.21.0 jupyter>=1.0 coverage==4.5.1
3.6
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
anyio==3.6.2
argon2-cffi==21.3.0
argon2-cffi-bindings==21.2.0
async-generator==1.10
attrs @ file:///opt/conda/conda-bld/attrs_1642510447205/work
Babel==2.11.0
backcall==0.2.0
bleach==4.1.0
certifi==2021.5.30
cffi==1.15.1
charset-normalizer==2.0.12
comm==0.1.4
contextvars==2.4
coverage==4.5.1
cycler==0.11.0
dataclasses==0.8
decorator==5.1.1
defusedxml==0.7.1
entrypoints==0.4
flake8==5.0.4
idna==3.10
immutables==0.19
importlib-metadata==4.2.0
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
ipykernel==5.5.6
ipython==7.16.3
ipython-genutils==0.2.0
ipywidgets==7.8.5
jedi==0.17.2
Jinja2==3.0.3
json5==0.9.16
jsonschema==3.2.0
jupyter==1.1.1
jupyter-client==7.1.2
jupyter-console==6.4.3
jupyter-core==4.9.2
jupyter-server==1.13.1
jupyterlab==3.2.9
jupyterlab-pygments==0.1.2
jupyterlab-server==2.10.3
jupyterlab_widgets==1.1.11
kiwisolver==1.3.1
MarkupSafe==2.0.1
matplotlib==2.2.3
mccabe==0.7.0
mistune==0.8.4
more-itertools @ file:///tmp/build/80754af9/more-itertools_1637733554872/work
nbclassic==0.3.5
nbclient==0.5.9
nbconvert==6.0.7
nbformat==5.1.3
nest-asyncio==1.6.0
notebook==6.4.10
numpy==1.19.5
packaging @ file:///tmp/build/80754af9/packaging_1637314298585/work
pandas==1.1.5
pandocfilters==1.5.1
parso==0.7.1
pexpect==4.9.0
pickleshare==0.7.5
pluggy @ file:///tmp/build/80754af9/pluggy_1615976315926/work
prometheus-client==0.17.1
prompt-toolkit==3.0.36
ptyprocess==0.7.0
py @ file:///opt/conda/conda-bld/py_1644396412707/work
pycodestyle==2.9.1
pycparser==2.21
pyflakes==2.5.0
Pygments==2.14.0
pyparsing @ file:///tmp/build/80754af9/pyparsing_1635766073266/work
pyrsistent==0.18.0
pytest==6.2.4
python-dateutil==2.9.0.post0
pytz==2025.2
PyYAML==6.0.1
pyzmq==25.1.2
requests==2.27.1
scipy==1.5.4
Send2Trash==1.8.3
-e git+https://github.com/CORE-GATECH-GROUP/serpent-tools.git@67846baca60f959ac92bdf208e6f1c6744688890#egg=serpentTools
six==1.17.0
sniffio==1.2.0
terminado==0.12.1
testpath==0.6.0
toml @ file:///tmp/build/80754af9/toml_1616166611790/work
tornado==6.1
traitlets==4.3.3
typing_extensions @ file:///opt/conda/conda-bld/typing_extensions_1647553014482/work
urllib3==1.26.20
wcwidth==0.2.13
webencodings==0.5.1
websocket-client==1.3.1
widgetsnbextension==3.6.10
zipp @ file:///tmp/build/80754af9/zipp_1633618647012/work

name: serpent-tools
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - attrs=21.4.0=pyhd3eb1b0_0
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - importlib_metadata=4.8.1=hd3eb1b0_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - more-itertools=8.12.0=pyhd3eb1b0_0
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - packaging=21.3=pyhd3eb1b0_0
  - pip=21.2.2=py36h06a4308_0
  - pluggy=0.13.1=py36h06a4308_0
  - py=1.11.0=pyhd3eb1b0_0
  - pyparsing=3.0.4=pyhd3eb1b0_0
  - pytest=6.2.4=py36h06a4308_2
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - toml=0.10.2=pyhd3eb1b0_0
  - typing_extensions=4.1.1=pyh06a4308_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zipp=3.6.0=pyhd3eb1b0_0
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - anyio==3.6.2
      - argon2-cffi==21.3.0
      - argon2-cffi-bindings==21.2.0
      - async-generator==1.10
      - babel==2.11.0
      - backcall==0.2.0
      - bleach==4.1.0
      - cffi==1.15.1
      - charset-normalizer==2.0.12
      - comm==0.1.4
      - contextvars==2.4
      - coverage==4.5.1
      - cycler==0.11.0
      - dataclasses==0.8
      - decorator==5.1.1
      - defusedxml==0.7.1
      - entrypoints==0.4
      - flake8==5.0.4
      - idna==3.10
      - immutables==0.19
      - importlib-metadata==4.2.0
      - ipykernel==5.5.6
      - ipython==7.16.3
      - ipython-genutils==0.2.0
      - ipywidgets==7.8.5
      - jedi==0.17.2
      - jinja2==3.0.3
      - json5==0.9.16
      - jsonschema==3.2.0
      - jupyter==1.1.1
      - jupyter-client==7.1.2
      - jupyter-console==6.4.3
      - jupyter-core==4.9.2
      - jupyter-server==1.13.1
      - jupyterlab==3.2.9
      - jupyterlab-pygments==0.1.2
      - jupyterlab-server==2.10.3
      - jupyterlab-widgets==1.1.11
      - kiwisolver==1.3.1
      - markupsafe==2.0.1
      - matplotlib==2.2.3
      - mccabe==0.7.0
      - mistune==0.8.4
      - nbclassic==0.3.5
      - nbclient==0.5.9
      - nbconvert==6.0.7
      - nbformat==5.1.3
      - nest-asyncio==1.6.0
      - notebook==6.4.10
      - numpy==1.19.5
      - pandas==1.1.5
      - pandocfilters==1.5.1
      - parso==0.7.1
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - prometheus-client==0.17.1
      - prompt-toolkit==3.0.36
      - ptyprocess==0.7.0
      - pycodestyle==2.9.1
      - pycparser==2.21
      - pyflakes==2.5.0
      - pygments==2.14.0
      - pyrsistent==0.18.0
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - pyyaml==6.0.1
      - pyzmq==25.1.2
      - requests==2.27.1
      - scipy==1.5.4
      - send2trash==1.8.3
      - six==1.17.0
      - sniffio==1.2.0
      - terminado==0.12.1
      - testpath==0.6.0
      - tornado==6.1
      - traitlets==4.3.3
      - urllib3==1.26.20
      - wcwidth==0.2.13
      - webencodings==0.5.1
      - websocket-client==1.3.1
      - widgetsnbextension==3.6.10
prefix: /opt/conda/envs/serpent-tools

serpentTools/tests/test_ResultsReader.py::RestrictedResultsReader::test_fluxAndKeff serpentTools/tests/test_ResultsReader.py::RestrictedResultsReader::test_justFlux
serpentTools/tests/test_ResultsReader.py::TestGetUniv::test_allVarsNone serpentTools/tests/test_ResultsReader.py::TestGetUniv::test_noUnivState serpentTools/tests/test_ResultsReader.py::TestGetUniv::test_nonPostiveIndex serpentTools/tests/test_ResultsReader.py::TestGetUniv::test_validUniv serpentTools/tests/test_ResultsReader.py::TestFilterResults::test_burnup serpentTools/tests/test_ResultsReader.py::TestFilterResults::test_metadata serpentTools/tests/test_ResultsReader.py::TestFilterResults::test_resdata serpentTools/tests/test_ResultsReader.py::TestFilterResults::test_universes serpentTools/tests/test_ResultsReader.py::TestFilterResults::test_varsMatchSettings serpentTools/tests/test_ResultsReader.py::TestFilterResultsNoBurnup::test_burnup serpentTools/tests/test_ResultsReader.py::TestFilterResultsNoBurnup::test_metadata serpentTools/tests/test_ResultsReader.py::TestFilterResultsNoBurnup::test_resdata serpentTools/tests/test_ResultsReader.py::TestFilterResultsNoBurnup::test_universes serpentTools/tests/test_ResultsReader.py::TestFilterResultsNoBurnup::test_varsMatchSettings serpentTools/tests/test_ResultsReader.py::TestResultsNoBurnNoGcu::test_burnup serpentTools/tests/test_ResultsReader.py::TestResultsNoBurnNoGcu::test_metadata serpentTools/tests/test_ResultsReader.py::TestResultsNoBurnNoGcu::test_resdata serpentTools/tests/test_ResultsReader.py::TestResultsNoBurnNoGcu::test_universes serpentTools/tests/test_ResultsReader.py::TestResultsNoBurnNoGcu::test_varsMatchSettings serpentTools/tests/test_ResultsReader.py::RestrictedResultsReader::test_xsGroups
serpentTools/tests/test_ResultsReader.py::TestBadFiles::test_emptyFile_noGcu serpentTools/tests/test_ResultsReader.py::TestBadFiles::test_noResults serpentTools/tests/test_ResultsReader.py::TestEmptyAttributes::test_emptyAttributes serpentTools/tests/test_ResultsReader.py::TestReadAllResults::test_burnup serpentTools/tests/test_ResultsReader.py::TestReadAllResults::test_metadata serpentTools/tests/test_ResultsReader.py::TestReadAllResults::test_resdata serpentTools/tests/test_ResultsReader.py::TestReadAllResults::test_universes serpentTools/tests/test_ResultsReader.py::TestReadAllResults::test_varsMatchSettings
serpentTools/parsers/results.py
serpentTools/parsers/results.py