Add missing return to g.setdefault

Author: ThiefMaster

flask/ctx.py

@@ -36,7 +36,7 @@ def pop(self, name, default=_sentinel):
             return self.__dict__.pop(name, default)
 
     def setdefault(self, name, default=None):
-        self.__dict__.setdefault(name, default)
+        return self.__dict__.setdefault(name, default)
 
     def __contains__(self, item):
         return item in self.__dict__