Merge tag 'v0.22.9'

release v0.22.9

src/db/plugins/ProxyDatabasePlugin.cxx

@@ -430,6 +430,7 @@ SendGroup(mpd_connection *connection, TagType group)
 	return mpd_search_add_group_tag(connection, tag);
 #else
 	(void)connection;
+	(void)group;
 
 	throw std::runtime_error("Grouping requires libmpdclient 2.12");
 #endif