First set the select formula option to 'use default values for nulls'.
if you don't it will stop evaluating when it hits a null, or you will have to alter the code to handle any possible null fields first.
your select should look something like this:
(
{?Status} = "(All)"
or
({?Status} = "(None)" and {audmmast.det_cde} IS NULL)
or
{audmmast.det_cde} = {?Status}
)
and
{audmrefs_rating.ref_typ} = "dda_cd5" and
{audmrefs_rating.fil_typ} = "150" and
{audmrefs_derived.fil_typ} = "150" and
{audmrefs_derived.ref_typ} = "dda_cd3" and
{audmrefs_dept.fil_typ} = "150" and
{audmrefs_dept.ref_typ} = "dda_cd1" and
{audmmast.doc_typ} = 150