Don't reference the 'event' element when creating a new row as the event...

... that triggered the content of an input changing may have been from another element.  The input should always be the current target.

I have an input area with a custom widget in plone, this widget is populated by a 'browse' button , as a result the 'event' that triggers the change of content on the input area has an element that is not the input itself.