RFR: 8194924: Checking for selection size before update

[Jeanette Winzenburg]

On Thu, 24 Jun 2021 11:29:23 GMT, Alexander Shaklein <github.com+26318329+cheesterx3 at openjdk.org> wrote:

> It is possible situation when `clearSelection()` is invoked during `onChange()` notify. In such case `selectedCellsSeq` is clearing and possible `IndexOutOfBoundsException` on `GenericAddRemoveChange` creation. 
> So we should check it to create correct `GenericAddRemoveChange`.

looks like a usage error to me, for multiple reasons:

in a listener to property changes of one property, we must not 

- access the state of another property (except we can guarantee the other to be completely orthogonal to the sender)
- change the state of the sender
- change the state of related properties

The example DavisSelectionTest in the report seems to do all of these ;)

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PR: https://git.openjdk.java.net/jfx/pull/542