IPP bistro parsing crashes

[COM8]

The IPP parser for the current week crashes, because there are no dishes on Wednesday available.
Link to the PDF.

The parser fails here

        positions = [(a.start(), a.end()) for a in list(re.finditer('Tagessuppe siehe Aushang', lines[0]))]
        if len(positions) != 5:
            # TODO handle special cases (e.g. that bistro is closed)
            return None

-> It returns None

How to reproduce:

$ python3 main.py ipp-bistro

Btw. I'm using #18 to fix the KW parsing crash.

[srehwald]

see #19