(change synopsis as you see fit)

SonarCloud reports a problem since JDK-8355003 integration.

Seems to unfold like this:

KlassTrainingData* KlassTrainingData::make(InstanceKlass* holder, bool null_if_not_found) {
  ...
}

...eventually calls:

  static KlassTrainingData* allocate(InstanceKlass* holder) {
    return TrainingData::allocate<KlassTrainingData>(holder);
  }

...which eventually calls:

KlassTrainingData::KlassTrainingData(InstanceKlass* klass) : TrainingData(klass) {
  if (holder() == klass) {
    return; // no change to make
  }

...which accesses:

  InstanceKlass* holder() const { return _holder; }

...but _holder is not yet initialized! So the check in KlassTrainingData::KlassTrainingData accesses garbage data.