RFR: 8370467: BorderFactory.createBevelBorder and createSoftBevelBorder throws NPE for null highlight and shadow [v5]

[Prasanta Sadhukhan]

> If we pass null as highlight and shadow color to `BorderFactory.createBevelBorder` and `createSoftBevelBorder`
> it throws NPE which is not mentioned in the spec as the expected outcome.
> Fixed the NPE and the spec

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

  javadoc

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27949/files
  - new: https://git.openjdk.org/jdk/pull/27949/files/2c018656..d8de38b3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27949&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27949&range=03-04

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/27949.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27949/head:pull/27949

PR: https://git.openjdk.org/jdk/pull/27949