command-not-fonud crashes if bad locale set in LANG

[Jarosław Kubik]

command_not_found_handler crashes when LANG is set to invalid value.

jaro@MACHINA2:~# LANG="pl_PL.utf8" fff
No command 'fff' found, did you mean:
 Command 'ffe' from package 'ffe' (universe)
 Command 'ffc' from package 'python-ffc' (universe)
 Command 'fnf' from package 'confluence' (universe)
 Command 'dff' from package 'dff' (universe)
 Command 'ftff' from package 'whichman' (universe)
fff: command not found
jaro@MACHINA2:~# LANG="pl_PL" fff
Sorry, command-not-found has crashed! Please file a bug report at:
https://bugs.launchpad.net/command-not-found/+filebug
Please include the following information with the report:

command-not-found version: 0.2.44