Fix failing Unit tests in many libraries

The following errors were fixed:
- SISIS: didn't recognize 0 results in some libraries (e.g. Bayreuth Uni)
- BiBer: didn't recognize 0 results in some libraries (e.g. Mülheim/Ruhr)
- iOPAC: didn't detect the search fields in Niebüll, because the have a different search form
- Aschaffenburg: `"rows_per_hit": 1 ` is no longer needed because there are now 2 rows per hit
- Düsseldorf: JSON file was invalid
- Fürth: URL was changed (but the old one still worked), which caused cookies not to be accepted
- Unit tests were failing in the unlikely case when the search query "harry" returns less than 3 results

also:
- fixed NullPointerException when getActivity() returned null when creating a MeaningDetector