RFR: 6257207: JTable.getDefaultEditor throws NullPointerException

[Prasanta Sadhukhan]

If getDefaultEditor() is called before the JTable model is setup, it results in NPE.

This is because when JTable sets its model, which ends up firing a table changed event. The testcase is listening for tableChanged events and querying the editor. But the editor isn't installed until after the model is set which results in NPE.
Fix is to ensure initializeLocalVars() which initializes default editor is setup before JTable sets its model.

No regression is observed in jtreg/jck testsuite with this change.

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Commit messages:
 - 6257207: JTable.getDefaultEditor throws NullPointerException
 - 6257207: JTable.getDefaultEditor throws NullPointerException
 - 6257207: JTable.getDefaultEditor throws NullPointerException

Changes: https://git.openjdk.org/jdk/pull/10871/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10871&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-6257207
  Stats: 134 lines in 2 files changed: 133 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10871.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10871/head:pull/10871

PR: https://git.openjdk.org/jdk/pull/10871