Fix textarea id see BT#15983

main/calendar/agenda_js.php

@@ -270,6 +270,7 @@ $form->addHtmlEditor(
     [
         'ToolbarSet' => 'TestProposedAnswer',
         'Height' => '120',
+        'id' => 'content'
     ]
 );
 

main/inc/lib/formvalidator/FormValidator.class.php

@@ -1028,6 +1028,7 @@ EOT;
         $attributes['cols'] = isset($config['cols']) ? $config['cols'] : 80;
         $attributes['cols-size'] = isset($config['cols-size']) ? $config['cols-size'] : [];
         $attributes['class'] = isset($config['class']) ? $config['class'] : [];
+        $attributes['id'] = isset($config['id']) ? $config['id'] : '';
 
         $this->addElement('html_editor', $name, $label, $attributes, $config);
         $this->applyFilter($name, 'trim');