RFR: 8340559: [premain] java process crash with -XX:+PrintTrainingInfo

[Dhamoder Nalla]

Java process crashes during training run with -XX:+PrintTrainingInfo as some of the _holder (i.e InstanceKlass and Method) objects are null in KlassTrainingData and MethodTrainingData.

repro command:
java -XX:+PrintTrainingInfo -XX:CacheDataStore=JavacBenchApp.cds -cp JavacBenchApp.jar JavacBenchApp 50

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

Commit messages:
 - [premain] java process crash with -XX:+PrintTrainingInfo

Changes: https://git.openjdk.org/leyden/pull/23/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=23&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340559
  Stats: 8 lines in 1 file changed: 3 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/leyden/pull/23.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/23/head:pull/23

PR: https://git.openjdk.org/leyden/pull/23