libobs: Add obs_group_or_scene_from_source()

Makes it a little bit easier to get a scene from either a source or
group.

libobs/obs.h

@@ -1772,6 +1772,13 @@ EXPORT void obs_sceneitem_group_enum_items(obs_sceneitem_t *group,
 /** Gets the group from its source, or NULL if not a group */
 EXPORT obs_scene_t *obs_group_from_source(const obs_source_t *source);
 
+static inline obs_scene_t *
+obs_group_or_scene_from_source(const obs_source_t *source)
+{
+	obs_scene_t *s = obs_scene_from_source(source);
+	return s ? s : obs_group_from_source(source);
+}
+
 EXPORT void obs_sceneitem_defer_group_resize_begin(obs_sceneitem_t *item);
 EXPORT void obs_sceneitem_defer_group_resize_end(obs_sceneitem_t *item);