Habpanel iFrame widget OpenHAB String Item Problem

Dear community,

I have a Twitter proxy that sends messages. For this reason I have defined a String Item and rules that handle the behavior. This works great.

String Tweet

However, I wanted to include the same information in the main screen of my Habpanel visualization. Therefore I created a widget iFrame:

When I run the widget in Firefox I’m getting this error message:

It works if I use a Dummy widget:

I have searched the resources for solution but found none.
Has anybody experienced the same problem before? Is it a known bug?

Running OpenHAB 2.2.0 release on openhabianpi.

If the item Tweet contains an URL you can use an iframe. If it contains just the Tweet, use dummy instead.