Fix widget.List layout when the items length is lower than the current visible ones, fixes #1864

[fpabl0]

Description:

Fixes #1864

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

[andydotxyz]

I think you've found why this is happening, but I don't think that scrolling to the top will always be desirable in this case.

[andydotxyz]

Thanks.
I have tested this more and it is a good fix to the crash - but there are still related issues, i.e. it seems to not correctly calculate how many items are visible:

[andydotxyz]

I think what I illustrated above is a separate issue, happy with this crash fix.

[fpabl0]

I have tested this more and it is a good fix to the crash - but there are still related issues, i.e. it seems to not correctly calculate how many items are visible:

Oh I see, is there a way to reproduce it? I have just remembered that issue but after this fix, I couldn't be able to reproduce again, so I though it was fixed too 🤔

[fpabl0]

@andydotxyz I have just realized you opened an issue about it.

Code to replicate is at #1864 - run it, choose 20, scroll to bottom then choose 10.

Exactly that was how I reproduced that issue before this fix. But after that, I am not able to reproduce 🤔

[fpabl0]

Update: I have been able to reproduce it again, I will comment on issue instead of here, to keep this organized.