RFR: 8296400: pointCrlIssuers might be null in DistributionPointFetcher::verifyURL

[Matthew Donovan]

Added null-checks for pointCrlIssuers before it is accessed.

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Commit messages:
 - 8296400: pointCrlIssuers might be null in DistributionPointFetcher::verifyURL

Changes: https://git.openjdk.org/jdk/pull/12866/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12866&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296400
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12866.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12866/head:pull/12866

PR: https://git.openjdk.org/jdk/pull/12866