RFR: 6529151: NullPointerException in swing.plaf.synth.SynthLookAndFeel$Handler [v3]

[Prasanta Sadhukhan]

> NPE is thrown for closed/disposed JDialogs after uninstalling the UI which is because for SynthEditorPaneUI even though is disposed of, Nimbus propertyHandler tries to get the style of this disposed component resulting in NPE, 
> which is fixed by a null check to prevent deferencing style object to get the color.

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  Test made headful

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10167/files
  - new: https://git.openjdk.org/jdk/pull/10167/files/f62d58b9..8c378448

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10167&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10167&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10167.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10167/head:pull/10167

PR: https://git.openjdk.org/jdk/pull/10167