[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...

sync_schema_props_perms('cw_source', syncprops=False)
add_attribute('CWSource', 'synchronizing')
if schema['BigInt'].eid is None:
    add_entity_type('BigInt')