Fix crash when applying mind control to vehicles

Closes issue #2816
What should happen when mind control is applied to vehicles?

--HG--
branch : trunk

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -3910,6 +3910,9 @@ void AuraEffect::HandleModPossessPet(AuraApplication const * aurApp, uint8 mode,
         if (caster->ToPlayer()->GetPet() != target)
             return;
 
+        if (target->IsVehicle()) //Avoid crash when mind controling vehicles due to an assert in Unit::SetCharmedBy
+            return;
+        
         target->SetCharmedBy(caster, CHARM_TYPE_POSSESS);
     }
     else