Index: trunk/packages/invirt-base/python/invirt/config.py
===================================================================
--- trunk/packages/invirt-base/python/invirt/config.py	(revision 1926)
+++ trunk/packages/invirt-base/python/invirt/config.py	(revision 1933)
@@ -21,4 +21,6 @@
     """Splice dict-tree d2 into d1.  Return d1.
 
+    d2 may be None for an empty dict-tree, because yaml.load produces that.
+
     Example:
     >>> d = {'a': {'b': 1}, 'c': 2}
@@ -28,4 +30,6 @@
     {'a': {'b', 1, 'd': 3}, 'c': 2}
     """
+    if d2 is None:
+        return d1
     for k in d2:
         if k in d1 and isinstance(d1[k], dict):