EditTranslation panel: if the default langauge is empty, do not show the complete link to the page instead

If editing a translation of a XWiki document, the "EditTranslation" panels is shown to the right, which tries to show a link to the document in the default language.

However as the default language is empty, the renderer decides to show the link instead, which is quite long and does not look nice.

This happens at the line

    $services.localization.render('panels.translation.editOriginalLanguage', ["[[${doc.defaultLanguage}>>path:$doc.getURL('edit', ""editor=${editor}&language=${doc.defaultLanguage}"")]]"])

Using "default" if ${doc.defaultLanguage} is empty helps to avoid this.