}
-NetworkError::NetworkError (string s, string d)
- : runtime_error (String::compose("%1 (%2)", s, d))
+NetworkError::NetworkError (string s, optional<string> d)
+ : runtime_error (String::compose("%1%2", s, d ? String::compose(" (%1)", *d) : ""))
, _summary (s)
, _detail (d)
{