RFR: 8258422: Cleanup unnecessary null comparison before instanceof check in java.base

[Andrey Turbanov]

8258422: Cleanup unnecessary null comparison before instanceof check in java.base

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Commit messages:
 - [PATCH] Cleanup unnecessary null comparison before instanceof check in java.base

Changes: https://git.openjdk.java.net/jdk/pull/20/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=20&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258422
  Stats: 42 lines in 21 files changed: 0 ins; 0 del; 42 mod
  Patch: https://git.openjdk.java.net/jdk/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/20/head:pull/20

PR: https://git.openjdk.java.net/jdk/pull/20