We've been getting a crash on WMFTooltipPresenting line self?.tooltipViewModels.removeFirst() on Xcode organizer. When the array is empty, is some cases, the system might try to execute this line.

Steps to reproduce

Fresh install the app on the device and enable tabs. Open the article view and click back fast. The tooltip can still be seen on screen when you get back to explore. The app crashes when you try to click the tooltip.

Test Steps

Test in 7.8.3.

1. Fresh install app on device and enable article tabs dev settings
2. After onboarding, tap featured article. After tapping "Got it" on first tooltip button, quickly tap the Back button.
3. App should not crash.
4. Go back to an article. You should see article tabs tooltips present.
5. Tap Got It to dismiss tooltips.
6. Go to another article, tooltips should not present.
7. Terminate app, launch again. Go to another article. Tooltips should not present.