Term Select: Unable to remove term only replace

[grappler]

When using term_select with 'multiple' => false, there is no option to remove the selected term just to override it.

When using 'multiple' => true, it is possible to remove the term but the value is then defined as null.

It would be good to be able to select "All terms".

This may apply to post_select too.

[goldenapples]

I was able to replicate. I think we should add a check in Shortcode.formatShortcode() to ensure that if a value is null, that attribute doesn't get output. Would that fix the issue?

It would be good to be able to select "All terms".

I've been thinking this over and I have a few questions:

• How should this be represented? Should we just add an option with a value of -1 and a name of "All terms" (or "All {taxonomy_plural_name}" if only one taxonomy is selected?
• What does this mean in the case of multiple taxonomies?
• Is there anything that having an "All terms"/"All posts" option would enable from a user standpoint that wouldn't be possible just by removing all the selections? Usually when I've used these fields, I've used them as a filter - like "show related posts, but limit to these these terms". In all the use cases I've come up with, having no value in the field is just as useful as a "Select all" value would be.

[grappler]

if a value is null, that attribute doesn't get output. Would that fix the issue?

Yes, this would fix it when multiple is enabled.

Removing the selection is only possible when multiple is enabled. It would work for me too just to have a blank option where nothing is selected.