asserting(s) is better than segfaulting if it turns out to be NULL later

svn:r16538

src/or/routerparse.c

@@ -2093,6 +2093,7 @@ networkstatus_parse_vote_from_string(const char *s, const char **eos_out,
   struct in_addr in;
   int i, inorder, n_signatures = 0;
   memarea_t *area = NULL, *rs_area = NULL;
+  tor_assert(s);
 
   if (router_get_networkstatus_v3_hash(s, ns_digest)) {
     log_warn(LD_DIR, "Unable to compute digest of network-status");