wayland: Release the SHM pool after initial cursor buffer creation

The backing memory will be automatically unmapped when the buffer objects are destroyed, so no need to keep the pool around.

src/video/wayland/SDL_waylandmouse.c

@@ -65,7 +65,6 @@ typedef struct
     int hot_x;
     int hot_y;
 
-    Wayland_SHMPool *shmPool;
     int images_per_frame;
     CustomCursorImage images[];
 } Wayland_CustomCursor;
@@ -736,6 +735,7 @@ static SDL_Cursor *Wayland_CreateAnimatedCursor(SDL_CursorFrameInfo *frames, int
     }
 
     SDL_CursorData *data = NULL;
+    Wayland_SHMPool *shm_pool = NULL;
     int pool_size = 0;
     int max_images = 0;
     bool is_stack = false;
@@ -773,8 +773,8 @@ static SDL_Cursor *Wayland_CreateAnimatedCursor(SDL_CursorFrameInfo *frames, int
         goto failed;
     }
 
-    data->cursor_data.custom.shmPool = Wayland_AllocSHMPool(pool_size);
-    if (!data->cursor_data.custom.shmPool) {
+    shm_pool = Wayland_AllocSHMPool(pool_size);
+    if (!shm_pool) {
         goto failed;
     }
 
@@ -812,7 +812,7 @@ static SDL_Cursor *Wayland_CreateAnimatedCursor(SDL_CursorFrameInfo *frames, int
             data->cursor_data.custom.images[offset + j].height = surface->h;
 
             void *buf_data;
-            data->cursor_data.custom.images[offset + j].buffer = Wayland_AllocBufferFromPool(data->cursor_data.custom.shmPool, surface->w, surface->h, &buf_data);
+            data->cursor_data.custom.images[offset + j].buffer = Wayland_AllocBufferFromPool(shm_pool, surface->w, surface->h, &buf_data);
             // Wayland requires premultiplied alpha for its surfaces.
             SDL_PremultiplyAlpha(surface->w, surface->h,
                                  surface->format, surface->pixels, surface->pitch,
@@ -828,12 +828,13 @@ static SDL_Cursor *Wayland_CreateAnimatedCursor(SDL_CursorFrameInfo *frames, int
     }
 
     SDL_small_free(surfaces, is_stack);
+    Wayland_ReleaseSHMPool(shm_pool);
 
     return cursor;
 
 failed:
+    Wayland_ReleaseSHMPool(shm_pool);
     if (data) {
-        Wayland_ReleaseSHMPool(data->cursor_data.custom.shmPool);
         SDL_free(data->frame_durations_ms);
         for (int i = 0; i < data->cursor_data.custom.images_per_frame * frame_count; ++i) {
             if (data->cursor_data.custom.images[i].buffer) {
@@ -922,8 +923,6 @@ static void Wayland_FreeCursorData(SDL_CursorData *d)
                 wl_buffer_destroy(d->cursor_data.custom.images[i].buffer);
             }
         }
-
-        Wayland_ReleaseSHMPool(d->cursor_data.custom.shmPool);
     }
 
     SDL_free(d->frame_durations_ms);