Find (and Search) result filters include null data

dontiknowyou

I have asked for this before. Here I ask again, in a more concrete form, with an image worth at least a few words. Here goes:

In both Find and Search results add no data or unknown to the results filters. Example: birth year. Many Family Tree profiles have no birth year. Some historical records (such as birth records) should have a birth year but don't.

If I could SQL query the database I could easily find these cases. But I must use the web interface. So please add this to the web interface.

(By the way, I tried to calculate N for this mock-up and got an unexpected result: 12932-(1+2+15+463+1781+4051+6468+277) = -126.)

(Please vote!)