I create RW cursor by selecting constant expression
I want to store NULL to the created field later
How to force cursor field to accept null values ?
ALTER TABLE c2 NULL cannot be used since real cursor contains some hundreds of columns need to allowed nul values and lot of rows.

Code to reproduce:

CREATE CURSOR test ( c1 char NULL )
APPEND BLANK

APPEND BLANK
SELECT  '' as c2 FROM test INTO CURSOR test1 readwrite
REPLACE c2 WITH null

Observed: program error
Field C2 does not accept null values.

Expected: no error