[hooks/syncschema] avoid altering a dropped table If the constraint's rdef is being removed, CWConstraintDelOp doesn't need to do anything. Otherwise it may try to alter a removed table/column. Closes #4154549

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