make OR not crash when non-OR connection dies

svn:r1319

src/or/rephist.c

@@ -131,6 +131,14 @@ void rep_hist_note_disconnect(const char* nickname, time_t when)
 void rep_hist_note_connection_died(const char* nickname, time_t when)
 {
   or_history_t *hist;
+  if(!nickname) {
+    /* XXX
+     * If conn has no nickname, it's either an OP, or it is an OR
+     * which didn't complete its handshake (or did and was unapproved).
+     * Ignore it. Is there anything better we could do?
+     */
+    return;
+  }
   hist = get_or_history(nickname);
   if (hist->up_since) {
     hist->uptime += (when - hist->up_since);