Core/Creature: restore previous behavior of random gender on respawn

Little regression added with 253c0f3d07e05557daa3ffdd4e2a2af4256fb65e

src/server/game/Entities/Creature/Creature.cpp

@@ -1768,7 +1768,11 @@ void Creature::Respawn(bool force)
         setDeathState(JUST_RESPAWNED);
 
         uint32 displayID = GetNativeDisplayId();
-        SetDisplayId(displayID);
+        if (sObjectMgr->GetCreatureModelRandomGender(&displayID))
+        {
+            SetDisplayId(displayID);
+            SetNativeDisplayId(displayID);
+        }
 
         GetMotionMaster()->InitDefault();
         //Re-initialize reactstate that could be altered by movementgenerators