There are a few newer ARIA attributes of type: string that I think should be allowed as empty:

• aria-braillelabel
• aria-brailleroledescription
• aria-valuetext

Since both aria-label and aria-roledescription are allowed to be empty, I see no reason why their braille equivalents shouldn't be. As for valuetext, it seems fairly reasonable that values can be empty, so aria-valuetext should be allowed empty too.