Use a proper NullTranslations instance instead of the class.
This should fix errors of this kind:
TypeError: unbound method ugettext() must be called with NullTranslations instance as first argument (got str instance instead)
See: #5958 Fix supplied by Shun-ichi Goto
Authored by: jruigrok 2008-02-03
Parent: [r6438]
Child: [r6440]
