Deleting user who has content locked
I had an issue with generic content.
A user was deleted who had content locked.
when browsing generic content under the content menu we received "Object reference not set to an instance of an object." alert messages.
returned 500 with this response: "Detail":"Object reference not set to an instance of an object." the ownr column in sf_content_items referred to a user that no longer existed. I assume when you are displaying "Locked by ......." on the page your user variable is null. updating the ownr field for the affected content item to a current user resolved the issue.
The problem is confirmed and logged for fixing - Bug #110685
the Telerik team
Just had this issue as well. We were able to restore the pages by going to Pages panel and selecting the "unlock page" option.