[repository] when deleting relations of a deleted external entity, we should skip non-crossable relation (closes #1973680)
elses this may lead to things as described in the ticket...
ifnotrql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',ask_confirm=False):rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',ask_confirm=False)