[jfx11u] RFR: 8284676: TreeTableView loses sort ordering when applied on empty table

[Ambarish Rapte]

Clean backport to jfx11u

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Commit messages:
 - 8284676: TreeTableView loses sort ordering when applied on empty table

Changes: https://git.openjdk.org/jfx11u/pull/108/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx11u&pr=108&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8284676
  Stats: 15 lines in 2 files changed: 14 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx11u/pull/108.diff
  Fetch: git fetch https://git.openjdk.org/jfx11u pull/108/head:pull/108

PR: https://git.openjdk.org/jfx11u/pull/108