updated frontend configuration check condition

Author: Marvin Kuhn

Resources/Private/UiPlugin/src/manifest.js

@@ -7,7 +7,7 @@ manifest('Breadlesscode.SimpleEditorExtend:UiPlugin', {}, (globalRegistry, { fro
     const ckEditorConfig = globalRegistry.get('ckEditor5').get('config');
     const buttonConfig = frontendConfiguration['Breadlesscode.SimpleEditorExtend:Buttons'];
 
-    if (!buttonConfig) {
+    if (!buttonConfig || typeof buttonConfig[Symbol.iterator] !== 'function') {
         return;
     }
 

Resources/Public/UiPlugin/Plugin.js

@@ -37305,7 +37305,7 @@ function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { de
     var ckEditorConfig = globalRegistry.get('ckEditor5').get('config');
     var buttonConfig = frontendConfiguration['Breadlesscode.SimpleEditorExtend:Buttons'];
 
-    if (!buttonConfig) {
+    if (!buttonConfig || typeof buttonConfig[Symbol.iterator] !== 'function') {
         return;
     }