RFR: 8371386: Fix potential NPE in SwingNode [v2]

[Prasanta Sadhukhan]

> There can be potential NPEs in SwingNode which is fixed

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

  Review comment

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1965/files
  - new: https://git.openjdk.org/jfx/pull/1965/files/a493c346..00196134

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1965&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1965&range=00-01

  Stats: 18 lines in 1 file changed: 7 ins; 9 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1965.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1965/head:pull/1965

PR: https://git.openjdk.org/jfx/pull/1965