Don't play default sample music when Chart Preview is active

lua handles this most of the time
the notefield pointer becomes null when preview is inactive, but also the bool should be false so it would exit before dereferencing null

src/Etterna/Screen/Others/ScreenSelectMusic.cpp

@@ -1425,7 +1425,10 @@ ScreenSelectMusic::AfterMusicChange()
 		if (SAMPLE_MUSIC_PREVIEW_MODE !=
 			SampleMusicPreviewMode_StartToPreview) {
 			if (!m_sSampleMusicToPlay.empty())
-				g_bSampleMusicWaiting = true;
+				// dont run basic preview if chart preview is running
+				// lua handles that stuff (we need to change that)
+				g_bSampleMusicWaiting = !(GAMESTATE->m_bIsChartPreviewActive &&
+										  m_pPreviewNoteField->IsVisible());
 		}
 	}