Ignore messages from unknown channels.
Ignore messages from unknown channels.

It occasionally happens that messages on a channel are received before
the subscription confirmation, which would cause a panic when looking
for the subscription.

Changed to simply ignore those.
XDjackieXD/librespot,joerg-krause/librespot,plietar/librespot,SimonPersson/librespot,michaelherger/librespot,michaelherger/librespot,plietar/librespot,XDjackieXD/librespot,bobbo/spotify-connect-scrobbler,plietar/spotify-connect,bobbo/spotify-connect-scrobbler,joerg-krause/librespot