whoops, fix seg fault i just introduced

svn:r3828

src/or/relay.c

@@ -407,7 +407,7 @@ int connection_edge_send_command(connection_t *fromconn, circuit_t *circ,
   relay_header_t rh;
   int cell_direction;
 
-  if (fromconn->marked_for_close) {
+  if (fromconn && fromconn->marked_for_close) {
     log_fn(LOG_WARN,"Bug: called on conn that's already marked for close at %s:%d.",
            fromconn->marked_for_close_file, fromconn->marked_for_close);
     return 0;