Core/Misc: minor typo and codestyle fixes

src/server/game/Maps/Map.cpp

@@ -3144,7 +3144,7 @@ bool InstanceMap::AddPlayerToMap(Player* player)
 
             // increase current instances (hourly limit)
             if (!group || !group->isLFGGroup())
-                player->AddInstanceEnterTime(GetInstanceId(), time(NULL));
+                player->AddInstanceEnterTime(GetInstanceId(), time(nullptr));
 
             // get or create an instance save for the map
             InstanceSave* mapSave = sInstanceSaveMgr->GetInstanceSave(GetInstanceId());