WYSIWYG editor does not load when editing events if the user limited edit rights

If a user has only edit rights on some calendars, but not on the main calendar space, loading the WYSIWYG-Editor when editing events failes.

Steps to reproduce:

1. remove edit rights to the "MoccaCalendar" space to the XWikiAllGroup
2. grant edit rights e.g. to the "MoccaCalendar.OtherEvents" subcalendar to the "XWikiAllGroup"
3. log in with a user without admin rights and go to the "MoccaCalendar" space
4. click on an event to open the detail view
5. click in the "Edit" button in the detail view to edit that event

Expected behavior:

• Dialog shows edit view and the "Description" loades the WYSIWYG editor

Actual behavior :

• Dialog shows edit view but the "Description" shows annotated HTML in a plain text area
• User need to go to "Other Events" calendar, or to the detailed view of that event to edit events with the WYSIWYG editor