RFR: 8247163: JFXPanel throws exception on click when no Scene is set

[Kevin Rushforth]

On Thu, 11 Jun 2020 00:34:20 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Fixing exception when clicking on JFXPanel when no Scene is set.
>> 
>> quick test: `./gradlew -PFULL_TEST=true -PUSE_ROBOT=true :systemTests: test --tests *javafx.embed.swing.JFXPan* --info`
>> 
>> It's a regression from my previous PR: https://github.com/openjdk/jfx/pull/25
>
> The fix looks correct to me (I haven't tested it yet). I left a minor comment inline.

The fix and test both look good. Approved pending the minor format change (no need for a second reviewer).

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PR: https://git.openjdk.java.net/jfx/pull/248