ART: Use ObjPtr for GetSuperClass

Bug: 37224696
Test: mmma art
Test: m test-art-host
Change-Id: If55db6e26bb1bb05a13c59b849bed17839fca6cf
diff --git a/openjdkjvmti/ti_heap.cc b/openjdkjvmti/ti_heap.cc
index 6c79a60..f19d0a0 100644
--- a/openjdkjvmti/ti_heap.cc
+++ b/openjdkjvmti/ti_heap.cc
@@ -1173,7 +1173,7 @@
     stop_reports_ = !ReportReferenceMaybeEnqueue(JVMTI_HEAP_REFERENCE_SUPERCLASS,
                                                  nullptr,
                                                  klass,
-                                                 klass->GetSuperClass());
+                                                 klass->GetSuperClass().Ptr());
     if (stop_reports_) {
       return;
     }