Fix another coverity-spotted memleak

src/or/control.c

@@ -2121,6 +2121,8 @@ handle_control_extendcircuit(control_connection_t *conn, uint32_t len,
   if (!zero_circ && !(circ = get_circ(smartlist_get(args,0)))) {
     connection_printf_to_buf(conn, "552 Unknown circuit \"%s\"\r\n",
                              (char*)smartlist_get(args, 0));
+    SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
+    smartlist_free(args);
     goto done;
   }