Fixed error in Powder's backfire message, fixed move disruption affecting recharge moves when it shouldn't, fixed error when Shell Side Arm has no targets, fixed AI not unregistering Mega Evolution if it won't do so after all

Data/Scripts/011_Battle/003_Move/008_MoveEffects_MoveAttributes.rb

@@ -1121,6 +1121,7 @@ class Battle::Move::CategoryDependsOnHigherDamagePoisonTarget < Battle::Move::Po
 
   def pbOnStartUse(user, targets)
     target = targets[0]
+    return if !target
     max_stage = Battle::Battler::STAT_STAGE_MAXIMUM
     stageMul = Battle::Battler::STAT_STAGE_MULTIPLIERS
     stageDiv = Battle::Battler::STAT_STAGE_DIVISORS