Don't setup TOR proxy unless TOR proxy address is specified on the command-line, otherwise a segfault occurs.

main.cpp

@@ -349,11 +349,13 @@ int main(int argc, char **argv) {
   setbuf(stdout, NULL);
   CDnsSeedOpts opts;
   opts.ParseCommandLine(argc, argv);
+  if (opts.tor) {
     CService service(opts.tor, 9050);
     if (service.IsValid()) {
       printf("Using Tor proxy at %s\n", service.ToStringIPPort().c_str());
       SetProxy(NET_TOR, service);
     }
+  }
   bool fDNS = true;
   if (!opts.ns) {
     printf("No nameserver set. Not starting DNS server.\n");