further simplify stringify

further simplify stringify

--- a/mercurial/templater.py	Wed Nov 15 15:51:58 2006 -0600
+++ b/mercurial/templater.py	Wed Nov 15 15:51:58 2006 -0600
@@ -156,8 +156,7 @@
 def stringify(thing):
     '''turn nested template iterator into string.'''
     if hasattr(thing, '__iter__'):
-        return "".join([stringify(t) for t in thing])
-    if thing is None: return ""
+        return "".join([stringify(t) for t in thing if t is not None])
     return str(thing)
 
 para_re = None