[jdk17u] RFR: 8268361: Fix the infinite loop in next_line

[Alex Kasko]

Clean backport of a minor fix. Testing: ran jtreg:jdk_management on Linux.

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Commit messages:
 - Backport 72672277e4dddf8e72f1c705cd5f57de40745635

Changes: https://git.openjdk.java.net/jdk17u/pull/130/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=130&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268361
  Stats: 15 lines in 1 file changed: 11 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/130.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/130/head:pull/130

PR: https://git.openjdk.java.net/jdk17u/pull/130