Fix errors on no participants initialized yet

Source/StudyFrameworkPlugin/Private/SFGameInstance.cpp

@@ -151,6 +151,7 @@ void USFGameInstance::OnWorldStart()
 void USFGameInstance::OnPostWorldCreation(UWorld* World)
 {
 	//this is actually called before BeginPlay but after EndPlay of the world before, so actually switch the current condition just here
+	if(Participant)
 		Participant->ApplyNextCondition();
 }