scan-build: get_proxy_addrport should always set its outputs

When get_proxy_addrport returned PROXY_NONE, it would leave
addr/port unset. This is inconsistent, and could (if we used the
function in a stupid way) lead to undefined behavior. Bugfix on
5b050a9b, though I don't think it affects tor-as-it-is.

src/or/connection.c

@@ -4814,6 +4814,8 @@ get_proxy_addrport(tor_addr_t *addr, uint16_t *port, int *proxy_type,
     }
   }
 
+  tor_addr_make_unspec(addr);
+  *port = 0;
   *proxy_type = PROXY_NONE;
   return 0;
 }