NULL_EXPRESSION   327 create.c           exp = crb_alloc_expression(NULL_EXPRESSION);
NULL_EXPRESSION   341 eval.c             case NULL_EXPRESSION:	/* FALLTHRU */
NULL_EXPRESSION   420 eval.c             case NULL_EXPRESSION:		/* FALLTHRU */
NULL_EXPRESSION  1406 eval.c             case NULL_EXPRESSION:
NULL_EXPRESSION   180 util.c             case NULL_EXPRESSION:	/* FALLTHRU */