RFR: 8299986: Wrong sublist used in ListChangeListener

[Andy Goryachev]

The obvious coding error has been corrected in two places.

No unit tests have been added because
a) the issue did not result in any apparent behavioral changes as it only affects  what is effectively cleanup
b) I found no easy way to construct a unit test without getting deep into implementation code

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Commit messages:
 - 8299986: Wrong sublist used in ListChangeListener

Changes: https://git.openjdk.org/jfx/pull/1029/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1029&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299986
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1029.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1029/head:pull/1029

PR: https://git.openjdk.org/jfx/pull/1029