RFR: 8306331: assert((cnt > 0.0f) && (prob > 0.0f)) failed: Bad frequency assignment in if

[Dean Long]

This change removes undefined behavior caused by signed overflow, which triggered an assert with Xcode14.3+1.0-beta1 on macos aarch64.

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Commit messages:
 - fix signed overflow

Changes: https://git.openjdk.org/jdk/pull/13551/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13551&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306331
  Stats: 26 lines in 1 file changed: 24 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13551.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13551/head:pull/13551

PR: https://git.openjdk.org/jdk/pull/13551