Fix bugs: i) check callback is non-null before calling in cleanup and (ii) prevent connection from being destructed before a main strand callback is invoked on it
Fix bugs: i) check callback is non-null before calling in cleanup and (ii) prevent connection from being destructed before a main strand callback is invoked on it

sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata