Fix "ghost" duplicates when sorting

[RobertoNegro]

Fixes issues #184 and #189 .

The key attribute should identify the row indifferently from its position.

[davidldear]

Would love to get this merged so we can make this better for our users.

[dannyklaassen]

Please add this fix. It is already open for a month now.

[Tarpsvo]

Heya! Thanks a ton for the PR! I added a fallback as well (${resourceName}-items-${resource.id?.value || index}) just in case. Maybe it might be necessary to use a composite instead, but I hope this will suffice. Will do some testing soon.

The new release is tagged 3.4.7.

Thanks again and good luck to you all!