libobs: Fix loading of custom_size for empty scenes

Previously, `custom_size` was checked at the end of the `scene_load`
function. If the scene contained no "items" array, the `custom_scene`
loading code would never be run.

This moves the `custom_size` code above the return statement.

(cherry picked from commit 018ce16703b4dfc384cbca7e6edec8c5ff03b9fb)

libobs/obs-scene.c

@@ -1103,6 +1103,12 @@ static void scene_load(void *data, obs_data_t *settings)
 
 	remove_all_items(scene);
 
+	if (obs_data_get_bool(settings, "custom_size")) {
+		scene->cx = (uint32_t)obs_data_get_int(settings, "cx");
+		scene->cy = (uint32_t)obs_data_get_int(settings, "cy");
+		scene->custom_size = true;
+	}
+
 	if (!items)
 		return;
 
@@ -1117,12 +1123,6 @@ static void scene_load(void *data, obs_data_t *settings)
 	if (obs_data_has_user_value(settings, "id_counter"))
 		scene->id_counter = obs_data_get_int(settings, "id_counter");
 
-	if (obs_data_get_bool(settings, "custom_size")) {
-		scene->cx = (uint32_t)obs_data_get_int(settings, "cx");
-		scene->cy = (uint32_t)obs_data_get_int(settings, "cy");
-		scene->custom_size = true;
-	}
-
 	obs_data_array_release(items);
 }