Slightly modify undefined check to make it match the rest of the codebase. No change in expected usage.

lib/util/ldaputil.js

@@ -60,7 +60,7 @@ module.exports.login = function(options, username, password) {
           })
         }
 
-    if (typeof options.search.filter !== 'undefined') {
+    if (options.search.filter) {
       var parsedFilter = ldap.parseFilter(options.search.filter)
       query.filter.filters.push(parsedFilter)
     }