Validate site icon URL

[crazytonyli]

I noticed there are many errors like this when navigating to the Reader.

Task <FF11E022-6F86-42FA-8041-1208EF01A307>.<10> finished with error [-1002] Error Domain=NSURLErrorDomain Code=-1002 "unsupported URL" UserInfo={NSLocalizedDescription=unsupported URL, NSErrorFailingURLStringKey=?d=404&s=80, NSErrorFailingURLKey=?d=404&s=80, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDataTask <FF11E022-6F86-42FA-8041-1208EF01A307>.<10>"
), _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <FF11E022-6F86-42FA-8041-1208EF01A307>.<10>, NSUnderlyingError=0x353ffa600 {Error Domain=kCFErrorDomainCFNetwork Code=-1002 "(null)"}}

The cause is URLSession fetches an incorrect URL ?d=404&s=80. It turns out some site icon urls are malformed.

The root cause is that readerSiteTopic.siteBlavatar is an empty string, which is used as a full URL path to construct a URL, which ends up to be ?d=404&s=80.

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.

Testing checklist:

• [ ] WordPress.com sites and self-hosted Jetpack sites.
• [ ] Portrait and landscape orientations.
• [ ] Light and dark modes.
• [ ] Fonts: Larger, smaller and bold text.
• [ ] High contrast.
• [ ] VoiceOver.
• [ ] 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)
• [ ] iPhone and iPad.
• [ ] Multi-tasking: Split view and Slide over. (iPad)

[wpmobilebot]

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

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23579-097ebc2
	Version	25.3
	Bundle ID	org.wordpress.alpha
	Commit	097ebc2593e4a94cc12dc1922f4e51c426458434
	App Center Build	WPiOS - One-Offs #10630

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[wpmobilebot]

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

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr23579-097ebc2
	Version	25.3
	Bundle ID	com.jetpack.alpha
	Commit	097ebc2593e4a94cc12dc1922f4e51c426458434
	App Center Build	jetpack-installable-builds #9673

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.