Fix a unicode crash in the admin language list
Prevent a crash when updating pootle-terminology.po

When the file does not exist on disk, accessing attributes on
self.file will fail. So check for that in advance. If this happens
on anything else than pootle-terminology.po, log a warning.

Fixes #3254
Always check for pootle_path in @get_path_obj
Accept any amount of args in get_overview_stats()

This works around decorator madness
Get default last action in case it is not set

Fixes #3240.