Bump to v4.13.0.

_arrayReduce.js

@@ -5,7 +5,7 @@ define([], function() {
    * iteratee shorthands.
    *
    * @private
-   * @param {Array} array The array to iterate over.
+   * @param {Array} [array] The array to iterate over.
    * @param {Function} iteratee The function invoked per iteration.
    * @param {*} [accumulator] The initial value.
    * @param {boolean} [initAccum] Specify using the first element of `array` as
@@ -14,7 +14,7 @@ define([], function() {
    */
   function arrayReduce(array, iteratee, accumulator, initAccum) {
     var index = -1,
-        length = array.length;
+        length = array ? array.length : 0;
 
     if (initAccum && length) {
       accumulator = array[++index];