Fix logout failure if active session was removed from room
Fix logout failure if active session was removed from room

If the user tries to immediately log out after being removed from a
conversation in which she was active an exception could be thrown during
the logout cleanup if no conversation is found for the session. If the
exception is not caught then the logout will fail.

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

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed