why do i get this error ?
INTERPRETE BUFFER = validation error for column ID_USER, value "***
null ***"


/*---
PREPARE STATEMENT
TR_HANDLE = 13648568
STMT_HANDLE = 13658704

INSERT INTO CONTINUT_RETETA_ETALON
( ID_RETETA
, ID_PRODUS
, PROCENT
, HISTEREZIS_UP
, HISTEREZIS_DOWN
, ID_USER)
VALUES
( ? /* CONTINUT_RETETA_ETALON.ID_RETETA */
, ? /* CONTINUT_RETETA_ETALON.ID_PRODUS */
, ? /* CONTINUT_RETETA_ETALON.PROCENT */
, ? /* CONTINUT_RETETA_ETALON.HISTEREZIS_UP */
, ? /* CONTINUT_RETETA_ETALON.HISTEREZIS_DOWN */
, ? /* CONTINUT_RETETA_ETALON.ID_USER */ )

FIELDS = [ Version 1 SQLd 0 SQLn 30 ]
----*/
/*---
EXECUTE STATEMENT
TR_HANDLE = 13648568
STMT_HANDLE = 13658704
PARAMS = [ Version 1 SQLd 6 SQLn 6
CONTINUT_RETETA_ETALON.ID_RETETA = 3
CONTINUT_RETETA_ETALON.ID_PRODUS = 111
CONTINUT_RETETA_ETALON.PROCENT = 11
CONTINUT_RETETA_ETALON.HISTEREZIS_UP = <NULL>
CONTINUT_RETETA_ETALON.HISTEREZIS_DOWN = <NULL>
CONTINUT_RETETA_ETALON.ID_USER = 2 ]

ERRCODE = 335544347
----*/
/*---
INTERPRETE BUFFER =

ERRCODE = 57
----*/
/*---
INTERPRETE BUFFER = validation error for column ID_USER, value "***
null ***"

ERRCODE = -1
----*/

/* Table: CONTINUT_RETETA_ETALON */

CREATE TABLE CONTINUT_RETETA_ETALON (
ID_RETETA LARGE_ID NOT NULL,
ID_PRODUS LARGE_ID NOT NULL,
PROCENT NUMERIC (2, 2) NOT NULL,
HISTEREZIS_UP NUMERIC (2, 2),
HISTEREZIS_DOWN NUMERIC (2, 2),
ID_USER LARGE_ID NOT NULL);



/* Check constraints definition */

ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##300" check (PROCENT > 0);
ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##301" check (ID_PRODUS > 0);


/* Primary keys definition */

ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##100" PRIMARY KEY (ID_RETETA,
ID_PRODUS);


/* Foreign keys definition */

ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##200" FOREIGN KEY (ID_RETETA)
REFERENCES RETETE_ETALON (ID_RETETA) ON DELETE CASCADE;
ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##201" FOREIGN KEY (ID_USER)
REFERENCES UTILIZATOR (ID_USER);
ALTER TABLE CONTINUT_RETETA_ETALON ADD
CONSTRAINT "CONTINUT_RETETA_ETALON##202" FOREIGN KEY (ID_PRODUS)
REFERENCES PRODUS_ABATOR (ID_PRODUS);


/* Indices definition */

CREATE UNIQUE INDEX "CONTINUT_RETETA_ETALON##100" ON
CONTINUT_RETETA_ETALON (ID_RETETA, ID_PRODUS);
CREATE INDEX "CONTINUT_RETETA_ETALON##200" ON CONTINUT_RETETA_ETALON
(ID_RETETA);
CREATE INDEX "CONTINUT_RETETA_ETALON##201" ON CONTINUT_RETETA_ETALON
(ID_USER);
CREATE INDEX "CONTINUT_RETETA_ETALON##202" ON CONTINUT_RETETA_ETALON
(ID_PRODUS);

SET TERM ^ ;