RFR: 6529151: NullPointerException in swing.plaf.synth.SynthLookAndFeel$Handler [v2]

[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 fix

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10167/files
  - new: https://git.openjdk.org/jdk/pull/10167/files/44cc6fbd..f62d58b9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10167&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10167&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 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