modules/mpd: take lock in waitForEvent to prevent SIGABORT

+ replaced deprecated MPD_IDLE_PLAYLIST with MPD_IDLE_QUEUE
+ add mutex for periodic_updater

include/modules/mpd.hpp

@@ -65,6 +65,9 @@ class MPD : public ALabel {
   unique_status status_;
   mpd_state     state_;
   unique_song   song_;
+
+  // To make sure the previous periodic_updater stops before creating a new one
+  std::mutex periodic_lock_;
 };
 
 }  // namespace waybar::modules