Handle 'not filled' fields better

[okdistribute]

Describe the idea
when using filters there is a problem, if the field is not filled then a point is excluded, can be an issue. Can something be made clearer to the user - that they might be missing a lot of observations Perhaps an option to choose ‘empty’ / not filled

What's your role? Where and how do you currently use the application?
tech @ dd

Have you thought about what it might look like?
Having a 'not filled' field would help people wanting to come back and verify and edit the data.
Maybe some way of showing which observations don't have the field filled.
Or maybe another view which shows all the greyed out observations too.

Additional context
Reported by NGO partners