[object-stats] Fix FeedbackVector stats collection

Bug: v8:7760
Change-Id: I975b467e46bed684e141c2a78a396de1072125f1
Reviewed-on: https://chromium-review.googlesource.com/1068894Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53310}

src/heap/object-stats.cc

@@ -593,6 +593,8 @@ void ObjectStatsCollectorImpl::RecordVirtualFeedbackVectorDetails(
     calculated_size += header_size;
 
     // Iterate over the feedback slots and log each one.
+    if (!vector->shared_function_info()->HasFeedbackMetadata()) return;
+
     FeedbackMetadataIterator it(vector->metadata());
     while (it.HasNext()) {
       FeedbackSlot slot = it.Next();