Prevent false positive from GCMole in DeferredFormatStackTrace.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index a1e2a48c0576afa7c86751fe327b9f3d550ecc8c..fbff7451a264e099d1f41d2c88e38873d3e780f4 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -7696,7 +7696,8 @@ void ErrorObjectList::DeferredFormatStackTrace(Isolate* isolate) {
       if (!getter_obj->IsJSFunction()) continue;
       getter_fun = JSFunction::cast(getter_obj);
       String* key = isolate->heap()->hidden_stack_trace_string();
-      if (key != getter_fun->GetHiddenProperty(key)) continue;
+      Object* value = getter_fun->GetHiddenProperty(key);
+      if (key != value) continue;
     }
 
     budget--;