[MailKit] MEMessageSecurityHandler primaryActionClicked crashes Mail when completionHandler called with nil

I'm working on a MailKit extension and I'm getting a full Mail crash every time I click the Primary Action button in my message banner.

I have filed a feedback: FB22513160

Apple's own unsubscribe banner successfully presents a confirmation modal when its primary action is clicked, demonstrating that this flow is intended to work. That behavior does not appear to be accessible to third-party extensions via the documented EMessageSecurityHandler API. Or if it is and I'm missing something, I'd love to know.

Thanks!

[MailKit] MEMessageSecurityHandler primaryActionClicked crashes Mail when completionHandler called with nil
 
 
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