Fix using the subscriber data channel when there is no publisher
Fix using the subscriber data channel when there is no publisher

When the HPB is used the data channel messages need to be sent through
the publisher peer. Due to a wrong condition if there was no publisher
peer they tried to be sent using the data channels of the subscribers,
but those messages were simply ignored.

Signed-off-by: Daniel Calviño Sánchez <bd7629e975cc0e00ea7cda4ab6a120f2ee42ac1b@gmail.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed