RFR: 8337783: Use THROW_NULL instead of THROW_0 in pointer contexts in misc runtime code

[Kim Barrett]

Please review this trivial change that, in misc. runtime code where a pointer
value is required, replaces uses of THROW_0 and THROW_MSG_0 with THROW_NULL
and THROW_MSG_NULL respectively.

Testing: mach5 tier1

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

Commit messages:
 - fix THROW_0 in runtime

Changes: https://git.openjdk.org/jdk/pull/20457/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20457&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337783
  Stats: 33 lines in 6 files changed: 0 ins; 0 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/20457.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20457/head:pull/20457

PR: https://git.openjdk.org/jdk/pull/20457