RFR: JDK-8263558: Possible NULL dereference in fast path arena free if ZapResourceArea is true [v2]

[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).

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  move check to caller; assert in AFree instead

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2995/files
  - new: https://git.openjdk.java.net/jdk/pull/2995/files/8181b61a..aab8bbfe

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2995&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2995&range=00-01

  Stats: 3 lines in 2 files changed: 1 ins; 0 del; 2 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