RFR: 8352420: [ubsan] codeBuffer.cpp:984:27: runtime error: applying non-zero offset 18446744073709486080 to null pointer

[Doug Simon]

This PR addresses undefined behavior in CodeBuffer by making `verify_section_allocation` return early for a partially initialized CodeBuffer.

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Commit messages:
 - short-circuit verify_section_allocation for partially initialized buffer

Changes: https://git.openjdk.org/jdk/pull/24118/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24118&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352420
  Stats: 3 lines in 2 files changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24118.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24118/head:pull/24118

PR: https://git.openjdk.org/jdk/pull/24118