Xinha External Link Mailto function doesn't work correct

When I add a clickable e-mailadress in the text I use the external link option.
In the pop-up screen I can change the default value 'http://' to 'mailto'
So far so good
But when I use the option 'toon in nieuw venster' the mailto option changes to the default value http
So the mailto function doesn't work.

I need to change the value again to 'mailto' before I can click on Oké

Can you fix this bug