Fix crash when pushing the same VC twice in Reader

[kean]

Fixes https://a8c.sentry.io/issues/3140539221.

It is as a workaround as I don't know how to reproduce it. Hopefully, it will become clearer once we get a full stack trace from wpAssertionFailure.

To test:

I verified that the fix works by calling safePushViewController twice.

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)

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 25.6 ❄️. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

Generated by 🚫 Danger

[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	pr23907-b00da1e
	Version	25.6
	Bundle ID	org.wordpress.alpha
	Commit	b00da1e
	App Center Build	WPiOS - One-Offs #11205

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

[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	pr23907-b00da1e
	Version	25.6
	Bundle ID	com.jetpack.alpha
	Commit	b00da1e
	App Center Build	jetpack-installable-builds #10243

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

[sentry-io]

Suspect Issues

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

• ‼️ NSInvalidArgumentException: <UINavigationController: 0x1083cde00> is pushing the same view controller instance (<_TtGC7SwiftU... ReaderPresenter.popMainNavigationController View Issue
• ‼️ NSInvalidArgumentException: <UINavigationController: 0x118031800> is pushing the same view controller instance (<WordPress.Re... ReaderPresenter.popMainNavigationController View Issue

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