Fix user import after #194 (import/export facilities)

Addendum to 43f5c002f0c45bbfa0fe4ef00862c099db9a66b5
Fixed 500 error which appeared when /i/* was opened.
Performance Optimization
Performance Optimization
New Solution
Removed unnecessary line
Redirect now works correct.
Added comment.
Merge remote-tracking branch 'richard/500to404' into develop
Better handling of /i/ (Closes https://github.com/hhucn/adhocracy.hhu_theme/issues/68)