Removing user and their projects caues an error

When using the option "Remove user" you can also delete projects of that user. After using this, I got an error.

{"reason":"Object of class [lcsb.mapviewer.model.user.User] with identifier [13]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [lcsb.mapviewer.model.user.User#13]","error-id":"998784a4-d791-4fba-837b-628013200ce4","error":"Internal server error."}