Ensure underscore build versions of _.where and _.findWhere align with Underscore 1.5.

Former-commit-id: 49653c65a29c5a9108630a38b80848b2e5596079

dist/lodash.underscore.js

@@ -2431,7 +2431,7 @@
    */
   function where(collection, properties, first) {
     return (first && isEmpty(properties))
-      ? null
+      ? undefined
       : (first ? find : filter)(collection, properties);
   }