Copy description when DnD variables from Globals in resources and configuration variable panels to POUs. Also prevent making exception in case some other DropSource wouldn't provide description.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType>
    <Linux/>
  </TargetType>
</BeremizRoot>