url: empty file URL should be parsed correctly

An empty file URL `file:` should be parsed to `file:///` instead of
`file://`. In the `kFile` state, the process was braked immediately
when the ch is EOL, but it should work as `default` in the kFile state
to adjust slashes.

src/node_url.cc

@@ -1074,8 +1074,10 @@ namespace url {
                   SET_HAVE_QUERY()
                   url.query = base.query;
                 }
+                break;
               }
-              break;
+              state = kPath;
+              continue;
             case '\\':
             case '/':
               state = kFileSlash;