RFR: JDK-8263558: Possible NULL dereference in fast path arena free if ZapResourceArea is true

[Thomas Stuefe]

Trivial.

Sonarcloud reports a possible NULL dereference when zapping the to-be-freed area in fast-path arena free. Possible call stack for this to happen starts in Node::destruct(PhaseValues* phase).

-------------

Commit messages:
 - start

Changes: https://git.openjdk.java.net/jdk/pull/2995/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2995&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263558
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2995.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2995/head:pull/2995

PR: https://git.openjdk.java.net/jdk/pull/2995