RFR: 8256397: MultipleSelectionModel throws IndexOutOfBoundException [v4]

[Florian Kirmaier]

> Fixing IndexOutOfBoundsException in the MultipleSelectionModelBase and added a unit-test for it.
> ticket: https://bugs.openjdk.java.net/browse/JDK-8256397
> run test: `./gradlew --continue -PFULL_TEST=true controls:test --tests "*MultipleSelectionModelImplTest*"`

Florian Kirmaier has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - Merge remote-tracking branch 'origjfx/master' into JDK-8256397
   
   # Conflicts:
   #	modules/javafx.controls/src/test/java/test/javafx/scene/control/MultipleSelectionModelImplTest.java
 - JDK_8256397
   Added a small test-factory, to test more cases
 - 8256397
   Fixing IndexOutOfBoundsException in the MultipleSelectionModelBase and added a unit-test for it.

-------------

Changes: https://git.openjdk.org/jfx/pull/353/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=353&range=03
  Stats: 29 lines in 2 files changed: 28 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/353.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/353/head:pull/353

PR: https://git.openjdk.org/jfx/pull/353