wayland: Prevent a possible crash when determining the display for a minimized window

A minimized window may not be associated with any displays, so check that the output array is valid and that there is at least one associated display before dereferencing.

Fixes a crash when attempting to unset fullscreen on a minimized window.

src/video/wayland/SDL_waylandwindow.c

@@ -494,9 +494,16 @@ static void FlushFullscreenEvents(SDL_Window *window)
 static void Wayland_move_window(SDL_Window *window)
 {
     SDL_WindowData *wind = window->driverdata;
-    SDL_DisplayData *display = wind->outputs[wind->num_outputs - 1];
+    SDL_DisplayData *display;
     SDL_DisplayID *displays;
 
+    if (wind->outputs && wind->num_outputs) {
+        display = wind->outputs[wind->num_outputs - 1];
+    } else {
+        /* A window may not be on any displays if minimized. */
+        return;
+    }
+
     displays = SDL_GetDisplays(NULL);
     if (displays) {
         for (int i = 0; displays[i]; ++i) {