[xwiki-users] exception during page deletion

When users deletes a page I get and page saying that I should wait until page is deleted. I check browser console and I see 500 response from xwiki and nothing happens. If I go to some parent page, I see that page is deleted. Checked xwiki log and see an exception: https://gist.github.com/edvorg/9519c5055011ecdb319f6dcbdee39a76 does anybody know why could it happen?