SOS's GCHeapsTraverse doesn't work for server GCs

[mikem8361]

The GCHeapsTraverse function doesn't work on my simple webapp that uses a server GC.

This is 7.0 Windows x64 target but it also doesn't on Linux or against a 6.0.6 runtime target process. The !dumpruntimetypes command is one that uses this function. The failing object below is all zeros with a null MethodTable.

0:000> !dumpruntimetypes
         Address           Domain               MT Type Name
------------------------------------------------------------------------------
curr_object:      000001398fc00020
----------------
Traversing a gc heap failed
0:000>

To repro just create a webapp and either attach live or create a full dump of it. I can also give you a dump that repros the problem.

@PeterSolMS, @cshung may one of you can look at this code to figure out why the traversal is going out of wack. The heaps are valid (VerifyHeap says so).

[cshung]

The bug is understood. The code in GCHeapTraverse missed the POH is empty case.