I have Meta Tags: Context enabled and I'm editing an existing tag (by path) via the module config (Configuration > Meta Tags)
When I edit the existing description and hit save, the meta description is updated.
However, if I delete the content in the field and hit save, the meta description does not update.
When I click to edit the tag again, the previous value is still in the meta description field.
Only when I delete the contents of the field and add a space will the meta description update as empty be hidden from the page source.