[lworld] RFR: 8373442: [lworld] Fix CDS heap dumping crashes

[Coleen Phillimore]

This fixes three crashes in when heap dumping is enabled with Matias's patch.
Tested with tier1-3, that doesn't exactly turn on valhalla and some --enable-valhalla testing locally.

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

Commit messages:
 - 8373442: [lworld] Fix CDS heap dumping crashes

Changes: https://git.openjdk.org/valhalla/pull/1784/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1784&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373442
  Stats: 83 lines in 8 files changed: 47 ins; 15 del; 21 mod
  Patch: https://git.openjdk.org/valhalla/pull/1784.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1784/head:pull/1784

PR: https://git.openjdk.org/valhalla/pull/1784