Trivia: Fix crash in /trivia qs
Trivia: Fix crash in /trivia qs

Previously, /trivia qs crashed if no questions had ever been added to the category.

sirDonovan/Pokemon-Showdown,Zarel/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,xfix/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,svivian/Pokemon-Showdown,Zarel/Pokemon-Showdown,Zarel/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown