url: fix building when using --without-intl

Fix compile bug when building with the --without-intl option
(introduced by 4b312387ea)

PR-URL: https://github.com/nodejs/node/pull/9041
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

src/node_url.cc

@@ -129,12 +129,12 @@ namespace url {
 #else
   // Intentional non-ops if ICU is not present.
   static int ToUnicode(std::string* input, std::string* output) {
-    output->reserve(input.length());
+    output->reserve(input->length());
     *output = input->c_str();
   }
 
   static int ToASCII(std::string* input, std::string* output) {
-    output->reserve(input.length());
+    output->reserve(input->length());
     *output = input->c_str();
   }