Fix Type::Intersect to allocate large enough union.

src/global-handles.cc

Index: src/global-handles.cc
diff --git a/src/global-handles.cc b/src/global-handles.cc
index e06f7948281fcb6fc95e364c9201266d0935fda1..6a871cfbee912824b37b24a0c4c78dd7d10ee1cc 100644
--- a/src/global-handles.cc
+++ b/src/global-handles.cc
@@ -626,7 +626,7 @@ bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
     // Once the entire group has been iterated over, set the object
     // group to NULL so it won't be processed again.
     delete entry;
-    object_groups_.at(i) = NULL;
+    object_groups_.Set(i, NULL);
   }
   object_groups_.Rewind(last);
   return any_group_was_visited;