fix(zlib) add check is callback is function

Add check is callback is function to prevent next error.
zlib.js:160
    callback(err);
    ^
TypeError: undefined is not a function
    at Unzip.onError (zlib.js:160:5)
    at Unzip.EventEmitter.emit (events.js:95:17)
    at Zlib._binding.onerror (zlib.js:298:10)