<Swing Dev> RFR: 5015261: JInternalFrame causes NPE [v4]

[Prasanta Sadhukhan]

> JInternalFrame.getDesktopIcon() can be null as setDesktopIcon() can be called with null value. There are many places in JInternalFrame where getDesktopIcon() is accessed without null check which might cause NPE. 
> Added null check for those cases.

Prasanta Sadhukhan has updated the pull request incrementally with two additional commits since the last revision:

 - Prevent null being set
 - Prevent null being set

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4989/files
  - new: https://git.openjdk.java.net/jdk/pull/4989/files/f69c24a1..3e1a444d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4989&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4989&range=02-03

  Stats: 8 lines in 1 file changed: 2 ins; 1 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4989.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4989/head:pull/4989

PR: https://git.openjdk.java.net/jdk/pull/4989