Hackadelic Discreet Text Widget
Discreet Text Widget is a generic lightweight solution to the Empty Widget Problem, and enables you to safely use SEO Table Of Contents in the sidebar in any theme. It can be used as a replacement for the default text widget, when it’s content is automatically delivered by a shortcode, and you want to hide the widget altogether when the content is empty.
It can be used in just the same way as the default WordPress text widget. Nothing more to say.