read_peer_msg: ignore errors not destined for this channel.

We quoted the spec, but somehow the implementation disappeared.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/read_peer_msg.c

@@ -85,6 +85,7 @@ u8 *read_peer_msg_(const tal_t *ctx,
 		 *    message:
 		 *    - MUST ignore the message.
 		 */
+		if (structeq(&chanid, channel) || channel_id_is_all(&chanid))
 			err_pkt(err, &chanid, arg);
 
 		return tal_free(msg);