Error cb is not a function

[robertsLando]

Here:

mqemitter/mqemitter.js

Lines 86 to 90 in 710d047

	if (this.closed) {
	return cb(new Error('mqemitter is closed'))
	}
	cb = cb || noop

cb = cb || noop should be done before that if

[mcollina]

PR?

[robertsLando]

Done #22