[9] Review request for 8051359 JPopupMenu creation in headless mode with JDK9b23 causes NPE

[Alexander Scherbatiy]

Hello,
Could you review the fix:
  bug: https://bugs.openjdk.java.net/browse/JDK-8051359
  webrev: http://cr.openjdk.java.net/~alexsch/8051359/webrev.00

  The fix avoids NPE throwing in headless mode.

  There are already regression tests that covers the issue in 
jdk/test/javax/swing/Headless folder.


Thanks,
Alexandr.