InvestigationReader fails to properly report missing sections at EOF

[sellth]

The ISA-tab i_file is pretty standardised in that all sections need to be included. Altamisa reports ParseIsatabException if during parsing an unexpected line is read i.e. a required section header is missing. If a section is missing at the end of the file however, an unrelated exception is thrown.

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/home/sellts_c/Code/altamisa/altamisa/isatab/parse_investigation.py", line 163, in read
    studies = list(self._read_studies())
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/sellts_c/Code/altamisa/altamisa/isatab/parse_investigation.py", line 393, in _read_studies
    contacts = tuple(self._read_study_contacts())
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/sellts_c/Code/altamisa/altamisa/isatab/parse_investigation.py", line 584, in _read_study_contacts
    if not line[0] == investigation_headers.STUDY_CONTACTS:  # pragma: no cover
           ~~~~^^^
TypeError: 'NoneType' object is not subscriptable

This is caused by Altamisa only checking for unexpected lines and not taking into account that missing sections at the end of file do not have any following lines.

[sellth]

fixed in #113