fix(CORE/CREATURE) Polymorphed erratic mob behavior (#5699)

src/server/game/Entities/Unit/Unit.cpp

@@ -9816,6 +9816,12 @@ bool Unit::Attack(Unit* victim, bool meleeAttack)
         return false;
     }
 
+    // creatures should not try to attack the player during polymorph
+    if (creature && creature->IsPolymorphed())
+    {
+        return false;
+    }
+
     //if (HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_PACIFIED)) // pussywizard: wtf? why having this flag prevents from entering combat? it should just prevent melee attack
     //    return false;