Fix uninitialized pending actions for Windows under Wayland

A windows pending actions wasn't cleared for new windows.
Although I'm not aware of user visible bugs, this prevents
unpredictable updates for new windows.

intern/ghost/intern/GHOST_WindowWayland.cc

@@ -319,7 +319,7 @@ struct GWL_Window {
    * These pending actions can't be performed when WAYLAND handlers are running from a thread.
    * Postpone their execution until the main thread can handle them.
    */
-  std::atomic<bool> pending_actions[PENDING_NUM];
+  std::atomic<bool> pending_actions[PENDING_NUM] = {false};
 #endif /* USE_EVENT_BACKGROUND_THREAD */
 };