For example, when document has been destroyed using
lok_doc_view_destroy_document()

Change-Id: I531b85018ffa25bcf88fb101c912b9f11b489a97
Reviewed-on: https://gerrit.libreoffice.org/20779Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>