[jdk18u] RFR: 8284548: Invalid XPath expression causes StringIndexOutOfBoundsException

[Ravi Reddy]

Clean backport of https://github.com/openjdk/jdk/commit/994f2e9271355bebf355279d0208c1d2054bab27 to jdk18u.

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Commit messages:
 - 8284548: Invalid XPath expression causes StringIndexOutOfBoundsException

Changes: https://git.openjdk.java.net/jdk18u/pull/102/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=102&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284548
  Stats: 86 lines in 2 files changed: 82 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/102.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/102/head:pull/102

PR: https://git.openjdk.java.net/jdk18u/pull/102