RFR: 8374444: Fix simple -Wzero-as-null-pointer-constant warnings [v2]

[Kim Barrett]

> Please review this trivial change to fix several recent changes that trigger
> `-Wzero-as-null-pointer-constant `warnings when that warning is enabled.
> 
> Testing: mach5 tier1

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  update copyrights

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29014/files
  - new: https://git.openjdk.org/jdk/pull/29014/files/5e9e059f..fe41f6ef

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29014&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29014&range=00-01

  Stats: 4 lines in 4 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/29014.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29014/head:pull/29014

PR: https://git.openjdk.org/jdk/pull/29014