src/xvba_video_glx.c: Do not leak mutex and cleanup glx_surface_unref

glx_output_surface_destroy did not destroy a mutex created in glx_output_surface_create. Rewrite surface_unref.

src/xvba_video_glx.c

@@ -803,8 +803,13 @@ glx_surface_unref(
     object_glx_surface_p obj_glx_surface
 )
 {
-    if (obj_glx_surface && --obj_glx_surface->refcount == 0)
+    if (!obj_glx_surface)
+        return;
+    --obj_glx_surface->refcount;
+    if (obj_glx_surface->refcount == 0) {
         destroy_glx_surface(driver_data, obj_glx_surface);
+        obj_glx_surface = NULL;
+    }
 }
 
 // References GLX surface
@@ -1839,6 +1844,9 @@ glx_output_surface_destroy(
             XFree(obj_output->gl_window.vi);
         obj_output->gl_window.vi = NULL;
     }
+
+    pthread_mutex_destroy(&obj_output->lock);
+
     free(obj_output);
 }