make VAAudiofileSignalSource more robust to not having a functioning VAServer connected

Source/VAPlugin/Private/SignalSources/VAAudiofileSignalSource.cpp

@@ -147,6 +147,10 @@ bool UVAAudiofileSignalSource::SetPlayBackPosition(const float Time)
 
 bool UVAAudiofileSignalSource::SetPlayAction(const int Action)
 {
+	if (!bInitialized)
+	{
+		return false;
+	}
 	InterallyStoredPlayAction = Action;
 	StorePlayStateInternallyEvent.Send(Action); //also send this to all slaves, so potentially still pending send numbers from GetPlayAction are overwritten