malcontent-control: Ignore a harmless error

This is a backport of
https://github.com/endlessm/gnome-control-center/pull/205 from Endless’
gnome-control-center fork, applied there after the code was copied over
here.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

malcontent-control/user-controls.c

@@ -328,10 +328,27 @@ update_app_filter (MctUserControls *self)
                                              &error);
 
   if (error)
+    {
+      /* It's expected that a non-admin user can't read another user's parental
+       * controls info unless the panel has been unlocked; ignore such an
+       * error.
+       */
+      if (act_user_get_uid (self->user) != getuid () &&
+          self->permission != NULL &&
+          !g_permission_get_allowed (self->permission) &&
+          g_error_matches (error, MCT_APP_FILTER_ERROR, MCT_APP_FILTER_ERROR_PERMISSION_DENIED))
+        {
+          g_clear_error (&error);
+          g_debug ("Not enough permissions to retrieve app filter for user '%s'",
+                   act_user_get_user_name (self->user));
+        }
+      else
         {
           g_warning ("Error retrieving app filter for user '%s': %s",
                      act_user_get_user_name (self->user),
                      error->message);
+        }
+
       return;
     }