Fingerprint result with force fpcalc is other than with default settings

Hello!
I'm developing an application using your library and I had the problem that I didn't get any result with the default fingerprinting. (`acoustid.match(self.__API_KEY, self.__file)`) :disappointed:
Then I used `acoustid.match(self.__API_KEY, self.__file, force_fpcalc=True)` and I received the data I needed. :+1:
Maybe you could take a look at this problem.
A possible solution would be setting fpcalc as the default finger printer.

PS: It also occurs using your aidmatch.py script

Start by reproducing the difference between acoustid.match(self.__API_KEY, self.__file) and the same call with force_fpcalc=True, then compare the related behavior in aidmatch.py. Done means the default fingerprinting path produces the expected result for the reported case, with the behavior covered by an appropriate test if the repository provides one.

Written by the indexing model from the issue text.