fix(XmppConnection): sendUnavailableBeacon
fix(XmppConnection): sendUnavailableBeacon

Copy/paste mistake - there's no such thing as this.connection in
the XmppConnection. Hard to track down because no error is logged.

jitsi/lib-jitsi-meet,damencho/lib-jitsi-meet,jitsi/lib-jitsi-meet,jiyeyuran/lib-jitsi-meet