Fix MultiIndex .loc "Too Many Indexers" with None as return value
- [x] closes #34318 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Three changes in indexing.py : 
- function _handle_lowerdim_multi_index_axis0 default return value was None, now it raises an Exception.
- function _getitem_lowerdim checks for a raised exception instead of a value None.
- function _getitem_nested_tuple checks for a raised exception instead of a value None(had to be changed because it also uses _handle_lowerdim_multi_index_axis0) 

