Currently, the way to "deselect" a select dropdown (such as the different options for entity types, or the filters in the filter form) is to select an empty row in the select.

This is actually not particularly good HTML - our filter forms for example fail to validate because "Element option without attribute label must not be empty", and I think our other forms only validate out of luck because of the non-breaking space we use being read differently by the validator depending on whether it's done by TT or React.

We should probably think of a better way to display this, ideally one that can be also understood normally by screen reader users. The way might not even be the same for all cases: some (like entity types) seem like they could use the empty option more explicitly being [none], while others (such as the forms) already have [none] entries to explicitly filter by whether the data is missing, and might be better shown as [no selection]?