Fix crash on tapping Account Settings menu for accounts with no sites

[staskus]

Fixes #19413

Description

Crash on tapping Account Settings menu for accounts with no sites. It happens because defaultBlog is nil.

Regression from Blog service lookup blog

Solution

Treat defaultBlog as an optional.

To avoid such issues in the future we could set nullable/nonnull attributes in WPAccount.h.

Testing instructions

Case 1:

1. Fresh install the app
2. Create a new account or login with an account with no sites created or added
3. Go to My Site
4. Click on Me (Avatar on the right top corner of the screen)
5. Click on Account Settings
6. It should open without a crash

Regression Notes

1. Potential unintended areas of impact

2. What I did to test those areas of impact (or what existing automated tests I relied on)

3. What automated tests I added (or what prevented me from doing so)

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[staskus]

@crazytonyli If you want and you can, feel free to take over this PR 👍 Thanks!

[staskus]

Also cherry-picked bundler fix #19409

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19418-d1b46eb on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19418-d1b46eb on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[crazytonyli]

Oops, thanks for fix this! I'll have a quick look to see if this is something that the compiler should warn us.

[mokagio]

@staskus this has been bundled as part of 20.9 beta 1 (20.9.0.1).

Thanks for your work 🙌