RFR: 8322239: [macos] a11y : java.lang.NullPointerException is thrown when focus is moved on the JTabbedPane [v4]

[Alexander Zuev]

> Add null check for the Aqua LnF situation when tab is hidden die to the tabs overflow.

Alexander Zuev has updated the pull request incrementally with one additional commit since the last revision:

  Moved frame disposal to the EDT

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17736/files
  - new: https://git.openjdk.org/jdk/pull/17736/files/126aa08b..aa380530

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17736&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17736&range=02-03

  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17736.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17736/head:pull/17736

PR: https://git.openjdk.org/jdk/pull/17736