Blank Optional DateRange omits Null Date values

This is very close to many other topics but not quite what I'm looking for.

I have an Optional date range param that is set up like this in my record selection.
(not(HasValue({?DateRange}))) OR ( isnull({Table.Date}) or {Table.Date} in {?DateRange} )

When the date range is entered, it runs records within that range as well as NULL dates. This works fine.
However, when the range is left blank, it only runs for non-NULL dates. If the date value is null, it get omitted from the results.

I have tried:
if HasValue({?DateRange}) then
   isnull({Table.Date}) or {Table.Date} in {?DateRange}
else true

As well as:
if HasValue({?DateRange}) then
   isnull({Table.Date}) or {Table.Date} in {?DateRange}
else
     isnull({Table.Date}) or not(isnull({Table.Date}) )


What can I do to get NULL dates when the param is left blank?

Thanks