IDML Filter: improve rainbow UI/UX for the thresholds of ignorance

The related issue ~~#756~~ has been solved with the focus on the filter code base. The UI/UX rainbow part remained unaccomplished to the full extent. I.e. a general error message is shown to a user when the threshold value is not valid.

It would be better to have a specific message for the field if an invalid value is entered (for more information on the already available code please refer to these changes).