Can't edit 'ad' widget 
When I attempt to edit the ad widget, I receive an error - this error occurs whether I'm trying to configure a new ad-spot or edit an already existing one (from before upgrading to 5.4.1)

When I attempt to edit the ad widget, I receive an error - this error occurs whether I'm trying to configure a new ad-spot or edit an already existing one (from before upgrading to 5.4.1)
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