“El is null” alert message in magento 1.5.1

When I tried to insert widget on cms page then there was error message el is null.


This is because of a forward slash is missing in lib/Varien/Data/Form/Element/Editor.php on line number 202.

Copy that Editor.php file in app/code/local/Lib/Varien/Data/Form/Element/

Replace following line

'onclick'   => "widgetTools.openDialog('" . $this->getConfig('widget_window_url') . "widget_target_id "

To

'onclick'   => "widgetTools.openDialog('" . $this->getConfig('widget_window_url') . "widget_target_id/"

After this change you can insert widget in cms.