Extra key in translation plugin interface

Hello, I am translating OJS to Serbian using translating Generic plugin in my installation of OJS. I use the latest version of OJS. When I want to delete extra key (see screenshot in attach.) it is not deleted after checking it and clcking on Save button. Please advise

The current development branch has this key as an XML singleton instead of an empty pair of opening/closing elements. I bet the deletion process isn’t smart enough to handle that.

You can delete this key from the XML file by hand.

This issue also appears in fa_IR.