`ted` module causes a crash when TED input file has no data rows

[mtiberti]

For instance:

(mavisp) teo@kb-bioinfo01:idps$ cat PCP4/simple_mode/ted/results.csv
TED_id,TED_boundaries,CATH_label

...
INFO:mavisp.core:processing module ted for PCP4, simple_mode
Traceback (most recent call last):
  File "/usr/local/envs/mavisp/bin/mavisp", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/usr/local/envs/mavisp/lib/python3.13/site-packages/mavisp/mavisp.py", line 150, in main
    mfs.ingest()
    ~~~~~~~~~~^^
  File "/usr/local/envs/mavisp/lib/python3.13/site-packages/mavisp/core.py", line 229, in ingest
    this_module.ingest(mutations['mutation'].tolist())
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/envs/mavisp/lib/python3.13/site-packages/mavisp/modules.py", line 2251, in ingest
    matching = ted_expanded[(ted_expanded['start'] <= resn) & (ted_expanded['end'] >= resn)]
                             ~~~~~~~~~~~~^^^^^^^^^
  File "/usr/local/envs/mavisp/lib/python3.13/site-packages/pandas/core/frame.py", line 4107, in __getitem__
    indexer = self.columns.get_loc(key)
  File "/usr/local/envs/mavisp/lib/python3.13/site-packages/pandas/core/indexes/range.py", line 417, in get_loc
    raise KeyError(key)
KeyError: 'start'

this happens for instance in protein PCP4, which is the current example for MAVISp_automatization idps mode, but can be just reproduced in any protein by modifying the results.csv TED file in the simple_mode/ted folder