Fix the crashes in UploadUtilsWrapper caused by null snackbarAttachView

[irfano]

Fixes #21010
I can't reproduce the crash, but it occurs when the activity is stopped while the snackbar is being invoked in a separate thread, such as in onActivityResult or EventBus functions. Therefore, I added a check before showing snackbars.

There are different crashes on Sentry related to UploadUtilsWrapper. If the snackbarAttachView is null, it's pointless to call functions showing snackbars. I made all snackbarAttachView parameters non-null and checked their nullability in the Java classes where these UploadUtilsWrapper' functions are being called.

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To Test:

Since I can't reproduce it, it's not testable.

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Regression Notes

1. Potential unintended areas of impact

   • None

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

   • N/A

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

   • Since I can't reproduce it, I didn't add a test.

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PR Submission Checklist:

• I have completed the Regression Notes.
• 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.

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Testing Checklist (strike-out the not-applying and unnecessary ones):

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• Talkback.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• Large and small screen sizes. (Tablet and smaller phones)
• Multi-tasking: Split screen and Pop-up view. (Android 10 or higher)

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 25.2. This milestone is due in less than 4 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

Generated by 🚫 Danger

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21012-59a69e6
	Commit	59a69e6
	Direct Download	jetpack-prototype-build-pr21012-59a69e6.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21012-59a69e6
	Commit	59a69e6
	Direct Download	wordpress-prototype-build-pr21012-59a69e6.apk

Note: Google Login is not supported on these builds.

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ ApplicationNotResponding: Background ANR org.wordpress.android.analytics.AnalyticsTracke... View Issue

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