Core/Units: no longer send collision height change packets when a player has not been added to the world yet

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

@@ -8192,7 +8192,8 @@ void Unit::Mount(uint32 mount, uint32 VehicleId, uint32 creatureEntry)
             if (charm->GetTypeId() == TYPEID_UNIT)
                 charm->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_STUNNED);
 
-        player->SendMovementSetCollisionHeight(player->GetCollisionHeight(), UPDATE_COLLISION_HEIGHT_MOUNT);
+        if (player->IsInWorld())
+            player->SendMovementSetCollisionHeight(player->GetCollisionHeight(), UPDATE_COLLISION_HEIGHT_MOUNT);
     }
 
     RemoveAurasWithInterruptFlags(SpellAuraInterruptFlags::Mount);