Passing a NULL pointer to a REF variable is allowed (with /vo7) but strongly discouraged.
You MUST make sure that the function being called does a check for NULL pointers for the REF parameter.
The following code shows how you should add a test to the function being called
FUNCTION Start() AS VOID
LOCAL n AS INT
n := 1
? TempRef(10 , n) // 11
? TempRef(10 , NULL) // 1976
RETURN
FUNCTION TempRef(a AS INT, r REF INT) AS INT
IF @r == NULL // Check for NULL pointer!
RETURN 1976
END IF
RETURN a + r
