[jdk17u-dev] RFR: 8286287: Reading file as UTF-16 causes Error which "shouldn't happen"

[Goetz Lindenmaier]

I backport this for parity with 17.0.8-oracle.

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Commit messages:
 - Backport cc7560e995eac56709d9e55a1561135fad246cb2

Changes: https://git.openjdk.org/jdk17u-dev/pull/1221/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1221&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286287
  Stats: 54 lines in 2 files changed: 52 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1221.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1221/head:pull/1221

PR: https://git.openjdk.org/jdk17u-dev/pull/1221