Mail app Delete (trashcan) button is no longer active after I view the sending email address

I get a lot of spam email so I have gotten into the habit of checking the sender email address by clicking the down carrot following the sender email address field. See the following screenshot. When I determine the email is from someone not associated with the ad in the email, it is clearly spam that should be deleted but the delete button is now no longer active and will not work again until I click on some other part of the email such as the margin. This is clearly a minor bug but I have been bothered by it for ages.