How do I remove a default image for listings with no image (getting fatal error)

On the Design -> Listings page in the GD settings, I uploaded an image to serve as the default image when no image is added for a listing.

Now I’m getting a fatal error when viewing the listing http://dev.prometheusfire.me/glorybody-development/places/canada/british-columbia/vancouver/vancouver-test/

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/teatrade/public_html/dev.prometheusfire.me/glorybody-development/wp-includes/formatting.php on line 703

I can’t go through a typical trouble shooting process because there is no built-in way to remove the default image. Clicking the button only allows me to replace it. Moreover, it isn’t even saved in the Media Library (it doesn’t show up there – isn’t this a bad practice? Shouldn’t this button be using the WP Media Library?)

I even went so far as to delete the image from the file directory, but now I just get a broken image on the page above since the URL is still assigned in the database. Where in the DB do I need to look to remove this? (I really should have to be doing database edits for something like this – can you improve this process).

None of this issue changes the fact that I’m getting that fatal error. This is all just to remove the image so that I can verify that the listing displays correctly without a default image assigned.