From ed99958d394d15e52102d3d103655509c7499e9e Mon Sep 17 00:00:00 2001
From: Martin Edenhofer <me@edenhofer.de>
Date: Fri, 26 Aug 2016 17:08:49 +0200
Subject: [PATCH] Improved keep_certain_attributes check.

---
 app/controllers/settings_controller.rb | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/app/controllers/settings_controller.rb b/app/controllers/settings_controller.rb
index ffee83cfe..e4bba300e 100644
--- a/app/controllers/settings_controller.rb
+++ b/app/controllers/settings_controller.rb
@@ -96,10 +96,12 @@ class SettingsController < ApplicationController
     [:name, :area, :state_initial, :frontend, :options].each { |key|
       params.delete(key)
     }
-    [:online_service_disable, :permission, :render].each { |key|
-      params[:preferences].delete(key)
-    }
-    params[:preferences].merge!(setting.preferences)
+    if !params[:preferences].empty?
+      [:online_service_disable, :permission, :render].each { |key|
+        params[:preferences].delete(key)
+      }
+      params[:preferences].merge!(setting.preferences)
+    end
     params
   end