This PR fixes 2 NPEs in Choice-and ComboBox, when the selection model is null.
ChoiceBox: - Null check in **valueProperty()** listener ComboBox: - Null check in **valueProperty()** listener - Null check in **ComboBoxListViewSkin#updateValue()** The tests checks, that no NPE is printed to the console (JUnit5 has the **assertDoesNotThrow​()** method, but 4 unfortunately has not). They also checks, that the set value is still displayed (either in the ComboBox button cell or the ChoiceBox display label) ------------- Commit messages: - 8089398: [ChoiceBox, ComboBox] throws NPE on setting value on null selectionModel Changes: https://git.openjdk.java.net/jfx/pull/557/files Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=557&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8089398 Stats: 71 lines in 5 files changed: 62 ins; 3 del; 6 mod Patch: https://git.openjdk.java.net/jfx/pull/557.diff Fetch: git fetch https://git.openjdk.java.net/jfx pull/557/head:pull/557 PR: https://git.openjdk.java.net/jfx/pull/557
