fixed bug:

ensure_unicode_string return None if 'string'
is type unicode

src/gtkgui_helpers.py

@@ -125,6 +125,7 @@ def escape_for_pango_markup(string):
 def ensure_unicode_string(string):
 	if type(string) == str:  
 		return unicode(string, encoding = 'utf-8')  
+	return string
 
 def autodetect_browser_mailer():
 	#recognize the environment for appropriate browser/mailer