[web/component] guard against invalid page_size form parameter
Same as dff28956f37e, except the almost same code exists in two places
(yay us).
sync_schema_props_perms('cwuri')
helper = repo.system_source.dbhelper
cu = session.cnxset.cu
helper.set_null_allowed(cu, 'moved_entities', 'extid', 'VARCHAR(256)', False)
commit()