Merge VHM fix from 2.6 branch

doc/CHANGES.txt

@@ -8,6 +8,8 @@ Zope Changes
 
     Bugs Fixed
 
+      - VirtualHostMonster handles empty Mapping paths properly.
+    
       - Deadlock prevention code added.
 
         It was possible for earlier versions of ZODB to deadlock when

lib/python/Products/SiteAccess/VirtualHostMonster.py

@@ -59,6 +59,7 @@ class VirtualHostMonster(Persistent, Item, Implicit):
                         while i2 < len(obpath) and obpath[i2][:4] == '_vh_':
                             i2 = i2 + 1
                         del obpath[i1:i2]
+                    if obpath:
                         try:
                             ob = self.unrestrictedTraverse(obpath)
                         except: