Core/SAI: Fix one startup error

src/server/game/AI/SmartScripts/SmartScriptMgr.cpp

@@ -1499,7 +1499,7 @@ bool SmartAIMgr::IsEventValid(SmartScriptHolder& e)
                 return false;
             }
 
-            if (phaseGroup && GetPhasesForGroup(phaseGroup))
+            if (!phaseGroup && GetPhasesForGroup(phaseGroup))
             {
                 TC_LOG_ERROR("sql.sql", "SmartScript: SMART_ACTION_SET_INGAME_PHASE_GROUP uses invalid phase group id %u for creature %u, skipped", phaseGroup, e.entryOrGuid);
                 return false;