mercurial/hgweb/webutil.py

--- a/mercurial/hgweb/webutil.py	Fri Mar 13 14:20:13 2015 -0400
+++ b/mercurial/hgweb/webutil.py	Fri Mar 13 17:00:06 2015 -0400
@@ -373,7 +373,10 @@
     diffopts = patch.diffopts(repo.ui, untrusted=True)
     if basectx is None:
         parents = ctx.parents()
-        node1 = parents and parents[0].node() or nullid
+        if parents:
+            node1 = parents[0].node()
+        else:
+            node1 = nullid
     else:
         node1 = basectx.node()
     node2 = ctx.node()