GameList: Prevent opening Properties multiple times for the same game

Source/Core/DolphinQt/Config/PropertiesDialog.h

@@ -17,6 +17,7 @@ class PropertiesDialog final : public StackedSettingsWindow
   Q_OBJECT
 public:
   explicit PropertiesDialog(QWidget* parent, const UICommon::GameFile& game);
+  const std::string& GetFilePath() const { return m_filepath; }
 
 signals:
   void OpenGeneralSettings();
@@ -24,4 +25,7 @@ signals:
 #ifdef USE_RETRO_ACHIEVEMENTS
   void OpenAchievementSettings();
 #endif  // USE_RETRO_ACHIEVEMENTS
+
+private:
+  const std::string m_filepath;
 };