Add hooks for activated / deactivated

[natemate90]

I'm getting the following error:
Uncaught TypeError: Cannot read property 'height' of null at VueComponent.updateInViewport (vendors-9734db2b5db5665331401bfd393f02d0.js:101585)

When using <keep-alive> to cache the <router-view> component, I believe there needs to be activated / deactivated hooks that make sure that the inViewportHandlers are added or removed

[SageSanyue]

Me too! Same error, but I can't delete 'keep-alive: true'.
So it displays error like:

index.js?fd90:204 Uncaught TypeError: Cannot read properties of null (reading 'bottom')
    at VueComponent.updateInViewport (index.js?fd90:204)

[BenjaminNolan]

@natemate90 @SageSanyue A PR which removes the listeners when the dom element is removed was merged in December, which I think should fix these issues. Might be worth re-checking with 3.1.0. :)