Hotfix (Error messages not shown)

Fixed error messages not being shown because of 'errchan' being nil

func NewServerMultiplex(errhdlr func(error)) *Multiplexer {
	return &Multiplexer{
		wg:      new(sync.WaitGroup),
		errhdlr: errhdlr,

                // Added this line
		errorch: make(chan error, 10),
	}
}

Additionaly, blocking errors have been solved during Stop()