(Issue 52) Bugfix for unexpected TypeError when maxLength rule receives undefined input

Author: DanielAlt-KWS

lib/rules/maxLength.js

@@ -6,7 +6,7 @@ module.exports = function maxLength({ attr, value, args }) {
     throw new Error(`Seed in maxLength rule for ${attr} must be a number.`);
   }
 
-  if (value.toString().length > parseInt(maxNum)) {
+  if (value && value.toString().length > parseInt(maxNum)) {
     return false;
   }