Possible 12.1.1 Bug: Site Themes Widget missing 'CustomizedDefaultDescription' language resource

I'm getting a Script Execution Error exception after updating to 12.1.1.20482 every time I enter the Theme Studio.

PRESENTED EXCEPTION: An error occurred while rendering the 'render-item.vm' script from the 'Themes' widget (db151d53-a9ed-4bbd-9d0f-602b90fedff1). (The Language Resource with identifier 'CustomizedDefaultDescription' could not be found.)

ORIGINAL EXCEPTION: Language resource 'CustomizedDefaultDescription' was not found.

Could someone please point me to where this language resource should reside and what the default English language text wants to be for it?