Closes #58: Deactivating the calendar in a workspace result in a 404 error

tracim/tracim/controllers/admin/workspace.py

         return DictLikeClass(result = dictified_workspace)
 
     @tg.expose('tracim.templates.workspace.edit')
-    def put(self, id, name, description, calendar_enabled):
+    def put(self, id, name, description, calendar_enabled=False):
         user = tmpl_context.current_user
         workspace_api_controller = WorkspaceApi(user)