FIX: Properly support defaults for upload site settings.

config/site_settings.yml

@@ -1,6 +1,6 @@
 # Available options:
 #
-# default            - The default value of the setting.
+# default            - The default value of the setting. For upload site settings, use the id of the upload seeded in db/fixtures/010_uploads.rb.
 # client             - Set to true if the javascript should have access to this setting's value.
 # refresh            - Set to true if clients should refresh when the setting is changed.
 # min                - For a string setting, the minimum length. For an integer setting, the minimum value.
@@ -48,14 +48,14 @@ required:
     default: ""
     type: username
   logo:
-    default: ""
+    default: -1
     client: true
     type: upload
   logo_url:
     hidden: true
     default: "/images/d-logo-sketch.png"
   logo_small:
-    default: ""
+    default: -2
     client: true
     type: upload
   logo_small_url:
@@ -83,14 +83,14 @@ required:
     hidden: true
     default: ""
   favicon:
-    default: ""
+    default: -3
     client: true
     type: upload
   favicon_url:
     hidden: true
     default: "/images/default-favicon.ico"
   apple_touch_icon:
-    default: ""
+    default: -4
     client: true
     type: upload
   apple_touch_icon_url: