Core/Maps: Fixed possible crash when resetting instances

src/server/game/Instances/InstanceSaveMgr.cpp

@@ -543,7 +543,10 @@ void InstanceSaveManager::_ResetInstance(uint32 mapid, uint32 instanceId)
     if (iMap && iMap->IsDungeon())
         ((InstanceMap*)iMap)->Reset(INSTANCE_RESET_RESPAWN_DELAY);
 
-    iMap->DeleteRespawnTimes();
+    if (iMap)
+        iMap->DeleteRespawnTimes();
+    else
+        Map::DeleteRespawnTimesInDB(mapid, instanceId);
 
     // Free up the instance id and allow it to be reused
     sMapMgr->FreeInstanceId(instanceId);