Don't call tty_free unless the client is a terminal, otherwise tty_init hasn't

been called and it may end up doing close(0). From Kalle Olavi Niemitalo.

server.c

@@ -915,6 +915,11 @@ server_lost_client(struct client *c)
 	}
 	log_debug("lost client %d", c->ibuf.fd);
 
+	/*
+	 * If CLIENT_TERMINAL hasn't been set, then tty_init hasn't been called
+	 * and tty_free might close an unrelated fd.
+	 */
+	if (c->flags & CLIENT_TERMINAL)
 		tty_free(&c->tty);
 
 	screen_free(&c->status);