Don't try to send something without path

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

mud.c

@@ -1394,7 +1394,7 @@ mud_send(struct mud *mud, const void *data, size_t size, int tc)
 
     mud_update(mud, now);
 
-    if (!size)
+    if (!size || !mud->count)
         return 0;
 
     if (size > sizeof(packet) - MUD_PACKET_MIN_SIZE) {