Fix nasty race condition with menu background audio. Fixes #12365

UI/GameInfoCache.cpp

@@ -734,6 +734,7 @@ void GameInfoCache::WaitUntilDone(std::shared_ptr<GameInfo> &info) {
 
 
 // Runs on the main thread. Only call from render() and similar, not update()!
+// Can also be called from the audio thread for menu background music.
 std::shared_ptr<GameInfo> GameInfoCache::GetInfo(Draw::DrawContext *draw, const std::string &gamePath, int wantFlags) {
 	std::shared_ptr<GameInfo> info;