[jdk17u-dev] RFR: 8313874: JNI NewWeakGlobalRef throws exception for null arg

[Oli Gillespie]

Nearly clean backport for https://bugs.openjdk.org/browse/JDK-8313874, the only difference is 17 using `NULL` compared to `nullptr` in tip required a manual (but trivial) merge.

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Commit messages:
 - Backport 028b3ae1b162bd8f7c340bfa6e9487ca83697955

Changes: https://git.openjdk.org/jdk17u-dev/pull/1688/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1688&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313874
  Stats: 11 lines in 2 files changed: 10 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1688.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1688/head:pull/1688

PR: https://git.openjdk.org/jdk17u-dev/pull/1688