RFR: 8089398: [ChoiceBox, ComboBox] throws NPE on setting value on null selectionModel [v3]

[Jeanette Winzenburg]

On Fri, 9 Jul 2021 09:46:04 GMT, Jeanette Winzenburg <fastegal at openjdk.org> wrote:

>````
>  // another test, exposing one of the NPEs in createList
>  ComboBox<String> comboBox = new ComboBox<>(items);
>  comboBox.setSelectionModel(null);
>  installDefaultSkin(comboBox);
> 

> the difference is that setup already installs a skin - so at the time of init the selectionModel still is available ;)

still failing 

> 
> The other access is in the listener to listView's selectedIndex .. it might be a bit tricky to expose in a test, I would go for a combo in a stage/loader, access the list and change its selectedIndex (maybe needs the popup open and/or firing a key onto it)

good fix and test :)

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PR: https://git.openjdk.java.net/jfx/pull/557