Closes: #8539

Description

Note: I'm tagging reviewers based on the author/reviewer of the related changes while the author isn't on the team anymore.

The crash

This PR aims to fix a recent crash in release 11.6 that I got to reproduce. The crash happens when the dashboard is showing the Add Product header, then the header is hidden like in landscape mode (the navigation bar is collapsed). Then, the dashboard content view gets replaced (e.g. when analytics is re-enabled) while the Auto Layout constraint that connects the header and the previous content view is being activated separately (DashboardViewController.observeNavigationBarHeightForHeaderVisibility).

The fix

To prevent the Auto Layout constraint from being activated when it includes a view that is being removed from the view hierarchy, the constraint is reset to nil before the content view is removed next. The constraint will be re-established in onDashboardUIUpdate's call to addViewBelowHeaderStackView for the new content view.

Testing instructions

Prerequisite: the Add Product banner is shown for the store

• Launch the app and log in to a store where the Add Product banner is shown --> the banner should be shown on the My store tab
• On web, go to the store's /wp-admin/admin.php?page=wc-settings&tab=advanced&section=features to disable analytics (uncheck Enables WooCommerce Analytics)
• In the app, pull to refresh the My store tab
• Rotate the screen to landscape mode and back to portrait mode --> the Add Product banner is not shown anymore
• On web, go to the store's /wp-admin/admin.php?page=wc-settings&tab=advanced&section=features to re-enable analytics (chcek Enables WooCommerce Analytics)
• In the app, pull to refresh the My store tab --> the app should not crash, and the Add Product banner is shown again above the analytics

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.