Fix GetObjectReferences API when caller doesn't zero the param (dotnet/coreclr#24299)

Commit migrated from https://github.com/dotnet/coreclr/commit/00a853313ee2943ce2e97e4e9e7a114e0e7bc689

src/coreclr/src/vm/proftoeeinterfaceimpl.cpp

@@ -6836,6 +6836,7 @@ HRESULT ProfToEEInterfaceImpl::GetObjectReferences(ObjectID objectId, ULONG32 cN
     {
         if (cNumReferences == 0)
         {
+            *pcNumReferences = 0;
             GCHeapUtilities::GetGCHeap()->DiagWalkObject(pBO, &CountContainedObjectRef, (void*)pcNumReferences);
         }
         else