use get for nested properties

Author: basz

addon/components/bs-form/element.js

@@ -1,13 +1,13 @@
 import BsFormElement from 'ember-bootstrap/components/bs-form/element';
-import { action } from '@ember/object';
+import { action, get } from '@ember/object';
 import { dependentKeyCompat } from '@ember/object/compat';
 
 export default class BsFormElementWithChangesetValidationsSupport extends BsFormElement {
   '__ember-bootstrap_subclass' = true;
 
   @dependentKeyCompat
   get errors() {
-    let error = this.model?.error?.[this.property]?.validation;
+    let error = get(this, `model.error.${this.property}.validation`);
     return error ? [error] : [];
   }