RFR: 8343622: AesDkCrypto.stringToKey should not return null [v4]

[Weijun Wang]

> When an exception happens inside these stringToKey() methods, it returns a null. This would lead to unexpected NPE some time in the future.

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  update copyright years

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21908/files
  - new: https://git.openjdk.org/jdk/pull/21908/files/48af1a25..5d33bf7c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21908&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21908&range=02-03

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21908.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21908/head:pull/21908

PR: https://git.openjdk.org/jdk/pull/21908