Don't start chall battle if cancelled
Don't start chall battle if cancelled

Challenge battles will no longer start if they've been cancelled after
being accepted, but before team validation completes.

xfix/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,Enigami/Pokemon-Showdown,Enigami/Pokemon-Showdown,svivian/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,panpawn/Gold-Server,xfix/Pokemon-Showdown,AustinXII/Pokemon-Showdown,Zarel/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,urkerab/Pokemon-Showdown,xfix/Pokemon-Showdown,panpawn/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,Enigami/Pokemon-Showdown,Enigami/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,panpawn/Gold-Server,AustinXII/Pokemon-Showdown,Zarel/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,svivian/Pokemon-Showdown,svivian/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,urkerab/Pokemon-Showdown,svivian/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,panpawn/Gold-Server,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,panpawn/Pokemon-Showdown,Zarel/Pokemon-Showdown,svivian/Pokemon-Showdown,AustinXII/Pokemon-Showdown,urkerab/Pokemon-Showdown