Incorrect metaspace statistics after JEP 387 when UseCompressedClassPointers is off

Reproduce:
 - run jdk/jfr/event/gc/heapsummary/TestHeapSummaryEventDefNewSerial.java with -XX:-UseCompressedClassPointers

For example, here is the incorrect metaspace statistics before the fix:
```
Event:jdk.MetaspaceSummary {
  startTime = 10:35:24.762
  gcId = 3
  when = "Before GC"
  gcThreshold = 21.0 MB
  metaspace = {
    committed = 10.3 MB
    used = 10.2 MB
    reserved = 16.0 MB
  }
  dataSpace = {
    committed = 10.3 MB
    used = 10.2 MB
    reserved = 16.0 MB
  }
  classSpace = {
    committed = 10.3 MB
    used = 10.2 MB
    reserved = 16.0 MB
  }
}
```