[jdk11u-dev] RFR: 8339470: [17u] More defensive fix for 8163921

[Dan Lutker]

Clean backport to fix regression in JDK11. Low risk and existing tests should be sufficient coverage.

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Commit messages:
 - Backport 6261dd7e3827ecd65c61a3d71f4234c88f08fccd

Changes: https://git.openjdk.org/jdk11u-dev/pull/2950/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2950&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339470
  Stats: 11 lines in 2 files changed: 1 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2950.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2950/head:pull/2950

PR: https://git.openjdk.org/jdk11u-dev/pull/2950