NULL_EXPRESSION   338 create.c           exp = crb_alloc_expression(NULL_EXPRESSION);
NULL_EXPRESSION   374 eval.c             case NULL_EXPRESSION:	/* FALLTHRU */
NULL_EXPRESSION   454 eval.c             case NULL_EXPRESSION:		/* FALLTHRU */
NULL_EXPRESSION  1693 eval.c             case NULL_EXPRESSION:
NULL_EXPRESSION   244 util.c             case NULL_EXPRESSION:	/* FALLTHRU */