start the php session before loading plugins in a standard manner (related to bug 2835: )

git-svn-id: http://piwigo.org/svn/trunk@20599 68402e56-0260-453c-a942-63ccdbb3a9ee

include/functions.inc.php

@@ -1621,10 +1621,6 @@ function get_branch_from_version($version)
  */
 function get_device()
 {
-  if (session_id() == '')
-  {
-    session_start();
-  }
   $device = pwg_get_session_var('device');
 
   if (is_null($device))
@@ -1661,11 +1657,6 @@ function mobile_theme()
     return false;
   }
 
-  if (session_id() == '')
-  {
-    session_start();
-  }
-
   if (isset($_GET['mobile']))
   {
     $is_mobile_theme = get_boolean($_GET['mobile']);