RFR: 8277497 Last column cell in the JTAble row is read as empty cell

[Artem Semenov]

Testing https://bugs.openjdk.java.net/browse/JDK-8271071 
Step to reproduce 
1) Run SwingSet2 in JDK 18 ( I used b24 ) 
2) Enable Voiceover. 
3) Select JTable demo 
4) Click any row in the table or select the first row . Observe that row is selected & VoiceOver reads the column values or navigate the columns one by one by pressing tab key. When the focus reaches the last column ( Favourite Food ) Observe that column value is read as null. If you hear the same then the bug is reproduced.

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Commit messages:
 - 8277497 Last column cell in the JTAble row is read as empty cell

Changes: https://git.openjdk.java.net/jdk/pull/6538/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6538&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277497
  Stats: 21 lines in 2 files changed: 12 ins; 8 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6538.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6538/head:pull/6538

PR: https://git.openjdk.java.net/jdk/pull/6538