[FIX] http: use default language when lang not in context

openerp/http.py

@@ -207,6 +207,7 @@ class WebRequest(object):
 
     @lazy_property
     def lang(self):
+        self.session._fix_lang(self.context)
         return self.context["lang"]
 
     @lazy_property
@@ -957,7 +958,7 @@ class OpenERPSession(werkzeug.contrib.sessions.Session):
 
         :param dict context: context to fix
         """
-        lang = context['lang']
+        lang = context.get('lang')
 
         # inane OpenERP locale
         if lang == 'ar_AR':