Hide options/values when no articles have this value

Thanks for this free module! Very useful.

Would it be possible to exclude items from the dropdown filed (in the filter module) when none of the article have that value set i the custom field? This would prevent the list being empty when a user selects an option in the list.

For example:
- There are 10 articles
- The article custom field has three values: red, blue and green.
- Some article have the option 'red'. Some have the option 'blue'.
- None of the articles have the option 'green'.

In the dropdown only 'red' and 'blue' options / choices are visible in this scenario.

When a new article is added that has the selected value of 'green' this option will be added to the dropdown.

Would that be possible?

Kind regards,
Jip