Standards.URI: Survive base URI's without authority sections.

Fixes "Bad argument 1 to sizeof()." for eg

  Standards.URI("<foo@example.com>", "mailto:<bar@example.com>");

lib/modules/Standards.pmod/URI.pike

@@ -280,7 +280,7 @@ void reparse_uri(this_program|string|void base_uri)
   // DWIM for "www.cnn.com" style input, when parsed in the context of
   // base "http://".
   if( !has_prefix(uri, "//") && !scheme && this::base_uri?->scheme &&
-      !sizeof(this::base_uri->authority) &&
+      !sizeof(this::base_uri->authority || "") &&
       !sizeof(this::base_uri->path))
   {
     DEBUG("DWIM authority: %O\n", uri);