fix missing HUD when starting on unrelated map crash

Source/StudyFrameworkPlugin/Private/HUD/SFMasterHUD.cpp

@@ -141,7 +141,7 @@ bool ASFMasterHUD::IsWidgetPresent() const
 
 void ASFMasterHUD::UpdateHUD(USFParticipant* Participant, const FString& Status)
 {
-	if (HUDWidget == nullptr) {
+	if (!HUDWidget) {
 		//store it and set it later on
 		UnForwardedParticipant = Participant;
 		UnforwardedStatus = Status;
@@ -173,11 +173,15 @@ void ASFMasterHUD::UpdateHUD(USFParticipant* Participant, const FString& Status)
 
 void ASFMasterHUD::AddLogMessage(const FString& Text)
 {
+	if (!HUDWidget)
+		return;
 	HUDWidget->AddLogMessage(Text);
 }
 
 void ASFMasterHUD::SetBackgroundColor(FLinearColor Color)
 {
+	if (!HUDWidget)
+		return;
 	HUDWidget->SetBackgoundColor(Color);
 }