lightningd: don't try to delete peer from db on shutdown if it's opening.

Fortunately, we hit the assert in wallet_peer_delete() if this happens,
since there are still active channels.

This latent bug becomes far more likely in followup patches, where
openingd is used for idle peers.

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

lightningd/lightningd.c

@@ -224,11 +224,16 @@ static void shutdown_subdaemons(struct lightningd *ld)
 		}
 
 		/* Freeing uncommitted channel will free peer. */
-		if (p->uncommitted_channel)
+		if (p->uncommitted_channel) {
-			tal_free(p->uncommitted_channel);
+			struct uncommitted_channel *uc = p->uncommitted_channel;
-		else
+
-			/* Removes itself from list as we free it */
+			/* Setting to NULL stops destroy_uncommitted_channel
-			tal_free(p);
+			 * from trying to remove peer from db! */
+			p->uncommitted_channel = NULL;
+			tal_free(uc);
+		}
+		/* Removes itself from list as we free it */
+		tal_free(p);
 	}
 	db_commit_transaction(ld->wallet->db);
 }

lightningd/opening_control.c

@@ -584,6 +584,10 @@ static void destroy_uncommitted_channel(struct uncommitted_channel *uc)
 		subd_release_channel(openingd, uc);
 	}
 
+	/* This is how shutdown_subdaemons tells us not to delete from db! */
+	if (!uc->peer->uncommitted_channel)
+		return;
+
 	uc->peer->uncommitted_channel = NULL;
 
 	maybe_delete_peer(uc->peer);