Fix file_matches to never return None
Fix file_matches to never return None

Should fix https://github.com/kivy/buildozer/issues/431#issuecomment-264732499 , as the deleted code just makes the function return None when presumably an empty list is fine and it should just continue.

Making a PR rather than a straight change in case I'm missing something about what's intended here.
rnixx/buildozer,inclement/buildozer,inclement/buildozer,kivy/buildozer,inclement/buildozer,kivy/buildozer,inclement/buildozer,rnixx/buildozer,rnixx/buildozer,kivy/buildozer,rnixx/buildozer,kivy/buildozer