PATCH: ActionErrors should use Collections.EMPTY_LIST - please review

[Matthias Kerkhoff <ma...@BESToffers.de>]

Attached is a minor modification to ActionErrors, that uses
Collections.EMPTY_LIST instead of the instance field empty_list.

This is a bit more efficient (there's no need to create the
empty list when creating an ActionErrors instance) and a bit
safer (no need to worry about modifications to the empty list,
because Collections.EMPTY_LIST is immutable) than the previous
version.

I would appreciate, if one of the contributors can have a look
at the source and do the check-in - I have no permissions.

-- 
Matthias                          mailto:make@BESToffers.de