[jfx17u] RFR: 8296413: Tree/TableView with null focus model throws NPE in queryAccessibleAttribute()

[Johan Vos]

Almost clean patch (apart from 3 (c) dates) for 
8296413: Tree/TableView with null focus model throws NPE in queryAccessibleAttribute()

Reviewed-by: arapte

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Commit messages:
 - 8296413: Tree/TableView with null focus model throws NPE in queryAccessibleAttribute()

Changes: https://git.openjdk.org/jfx17u/pull/124/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx17u&pr=124&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296413
  Stats: 235 lines in 8 files changed: 181 ins; 26 del; 28 mod
  Patch: https://git.openjdk.org/jfx17u/pull/124.diff
  Fetch: git fetch https://git.openjdk.org/jfx17u pull/124/head:pull/124

PR: https://git.openjdk.org/jfx17u/pull/124