[jdk21u] RFR: 8312612: handle WideCharToMultiByte return values

[Matthias Baesken]

8312612: handle WideCharToMultiByte return values

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Commit messages:
 - Backport d9559f9b24ee76c074cefcaf256d11ef5a7cc5b7

Changes: https://git.openjdk.org/jdk21u/pull/188/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=188&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312612
  Stats: 32 lines in 3 files changed: 19 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk21u/pull/188.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/188/head:pull/188

PR: https://git.openjdk.org/jdk21u/pull/188