url: fix off-by-one error in loop handling dots

Fixes an error where a loop, used to traverse an array of length `n`,
ran `n + 1` times instead of `n`.

PR-URL: #8420
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

lib/url.js

@@ -847,7 +847,7 @@ Url.prototype.resolveObject = function(relative) {
   // strip single dots, resolve double dots to parent dir
   // if the path tries to go above the root, `up` ends up > 0
   var up = 0;
-  for (var i = srcPath.length; i >= 0; i--) {
+  for (var i = srcPath.length - 1; i >= 0; i--) {
     last = srcPath[i];
     if (last === '.') {
       spliceOne(srcPath, i);