For the default editor fieds, the value " - - - " is missing

Here : http://localhost:8080/xwiki/bin/edit/XWiki/XWikiPreferences?editor=object

For the default editor fieds, the value " - - - " is missing, only "Test" or "Wysiwyg" is available.

This missing value lead to incoherent behaviour like : a basic user is unable to edit a page in wysiwyg even though the value of the field is set on "Wysiwyg"...

Thanks.