--- pydot-1.0.25/pydot.py	2011-10-09 18:07:19.345585402 +0200
+++ pydot-1.0.25/pydot.py	2011-10-09 18:08:05.764531832 +0200
@@ -591,7 +591,10 @@
             if default_node_name in ('subgraph', 'digraph', 'cluster'):
                 default_node_name = 'graph'
                 
-            defaults = self.get_parent_graph().get_node( default_node_name )
+            try:
+            	defaults = self.get_parent_graph().get_node( default_node_name )
+            except AttributeError:
+                defaults = None
             
             # Multiple defaults could be set by having repeated 'graph [...]'
             # 'node [...]', 'edge [...]' statements. In such case, if the
@@ -605,7 +608,10 @@
                 defaults = [defaults]
                 
             for default in defaults:
-                attr_val = default.obj_dict['attributes'].get(attr, None)
+                try:
+                    attr_val = default.obj_dict['attributes'].get(attr, None)
+                except AttributeError:
+                    attr_val = None
                 if attr_val:
                     return attr_val
         else: