BUG: pd.concat coerces ints to floats if empty DataFrame is present with different columns
- I have checked that this issue has not already been reported.

- I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---
**Note** This issue is very similar to [Issue #8902](https://github.com/pandas-dev/pandas/issues/8902), which is fixed in `pandas==1.3.0`, but in cases where the DataFrame to concat has different columns settings as stated below, `pd.concat` is still acting weird?


#### 
```python
import pandas as pd

# pd.concat with empty DataFrame won't coerce type now 
df = pd.DataFrame([{"col1": 1}, {"col1":2}])
df2 = pd.DataFrame({})
df_new = pd.concat([df,df2])
df_new.col1.dtype # dtype('int64')

# however, pd.concat with empty DataFrame with column different than the original one will still coerce type
df = pd.DataFrame([{"col1": 1}, {"col1":2}])
df2 = pd.DataFrame({}, columns=["whatever"])
df_new = pd.concat([df,df2])
df_new.col1.dtype # dtype('float64')

# pd.concat with empty DataFrame with same columns will still coerce type to `object`
df = pd.DataFrame([{"col1": 1}, {"col1":2}])
df2 = pd.DataFrame({}, columns=["col1"])
df_new = pd.concat([df,df2])
df_new.col1.dtype # dtype('object')
```

#### Problem description

`pd.concat` is acting inconsistently when concatenating empty DataFrame: 
If the empty DataFrame is present with same column, that column is changed to `dtype('O')`;
If the empty DataFrame is present with columns different than target, the target DataFrame has its original column values of type `int64` coerced to `float64`;
If the empty DataFrame is present without any column, the target DataFrame keeps its dtype;

#### Expected Output

I suggest just not coerce values when `pd.concat` an empty DataFrame...

#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit           : f00ed8f47020034e752baf0250483053340971b0
python           : 3.9.2.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.14.81.bm.15-amd64
Version          : #1 SMP Debian 4.14.81.bm.15 Sun Sep 8 05:02:31 UTC 2019
machine          : x86_64
processor        : 
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.3.0
numpy            : 1.19.2
pytz             : 2021.1
dateutil         : 2.8.1
pip              : 21.0.1
setuptools       : 49.6.0.post20210108
Cython           : 0.29.23
pytest           : 6.2.4
hypothesis       : None
sphinx           : 3.5.4
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : 0.9.2
psycopg2         : None
jinja2           : 2.11.3
IPython          : 7.22.0
pandas_datareader: None
bs4              : 4.9.3
bottleneck       : None
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : 3.4.2
numexpr          : None
odfpy            : None
openpyxl         : 3.0.7
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : None
sqlalchemy       : 1.4.20
tables           : None
tabulate         : 0.8.9
xarray           : None
xlrd             : 2.0.1
xlwt             : None
numba            : None
</details>
