plugin: fix CultureInfo null param exception
plugin: fix CultureInfo null param exception

This was introduced in #3272.  This is just a quick fix and
not a proper one.

Fixes #3306, #3307.

quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot