fix: Notification crash in destructor on app quit

[codebytere]

Description of Change

Closes #19842.
Closes #18701.

Previously, when you close the api notification, that notification forgets about the platform notification. As such, when it is destroyed it will not call set_delegate(nullptr). The notification can be reset here without the delegate having been reset, which creates the conditions necessary for this crash. This PR fixes that by ensuring that the delegate is always set to nullptr before the notification is reset.

cc @MarshallOfSound @nornagon

h/t to @charlag for great work investigating this!

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed a crash that would occur when Notifications were closed in concert with app termination.

[nornagon]

Seems a bit fishy to me that setting the delegate to nullptr on an object that is then immediately destroyed would change behavior. Is the notification being used after having been freed..?

[codebytere]

@nornagon see #19842 (comment) for more context :)

[nornagon]

ah, I missed that notification_ here is a WeakPtr and not a unique_ptr.

[release-clerk]

Release Notes Persisted

Fixed a crash that would occur when Notifications were closed in concert with app termination.

[trop]

I have automatically backported this PR to "6-1-x", please check out #21718

[trop]

I have automatically backported this PR to "7-1-x", please check out #21719

[trop]

I have automatically backported this PR to "8-x-y", please check out #21720