Correct error handling when no message is defined.

FossilOrigin-Name: 964d457584bbfbb9399a162faafd12b29a1e2f18f09ee4d3ec98aaaba6af9f19

src/cw/send.c

@@ -76,8 +76,10 @@ int conn_send_msg(struct conn * conn, uint8_t *rawmsg)
 int cw_send_request(struct conn *conn,int msg_id)
 {
 	cw_init_request(conn, msg_id);
-	if ( cw_put_msg(conn, conn->req_buffer) == -1 )
-		return 0;
+	if ( cw_put_msg(conn, conn->req_buffer) == -1 ){
+		errno=ENOMSG;
+		return -1;
+	}
 	conn_send_msg(conn, conn->req_buffer);