tipc: Convert fatal broadcast sanity check to non-fatal check

Modifies the existing broadcast link sanity check that detects an
attempt to send a message off-node when there are no available
destinations so that it no longer causes a kernel panic; instead,
the check now issues a warning and stack trace and then returns
without sending the message anywhere.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/bcast.c

@@ -552,12 +552,16 @@ static int tipc_bcbearer_send(struct sk_buff *buf,
 	if (likely(!msg_non_seq(buf_msg(buf)))) {
 		struct tipc_msg *msg;
 
-		assert(tipc_bcast_nmap.count != 0);
 		bcbuf_set_acks(buf, tipc_bcast_nmap.count);
 		msg = buf_msg(buf);
 		msg_set_non_seq(msg, 1);
 		msg_set_mc_netid(msg, tipc_net_id);
 		bcl->stats.sent_info++;
+
+		if (WARN_ON(!tipc_bcast_nmap.count)) {
+			dump_stack();
+			return 0;
+		}
 	}
 
 	/* Send buffer over bearers until all targets reached */