Bump to v4.16.5.

unionWith.js

@@ -27,9 +27,7 @@ import last from './last.js';
  */
 var unionWith = baseRest(function(arrays) {
   var comparator = last(arrays);
-  if (isArrayLikeObject(comparator)) {
-    comparator = undefined;
-  }
+  comparator = typeof comparator == 'function' ? comparator : undefined;
   return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), undefined, comparator);
 });