Use default skin on login page, also after logout

Before we stored user skin in session to keep user skin on logon after logout.
After more thinking... imho it's better to always present the same logon look.

program/include/rcmail.php

@@ -100,6 +100,9 @@ class rcmail extends rcube
         $required_plugins = array('filesystem_attachments', 'jqueryui');
         $this->plugins->load_plugins($plugins, $required_plugins);
 
+        // Remember default skin, before it's replaced by user prefs
+        $this->default_skin = $this->config->get('skin');
+
         // start session
         $this->session_init();
 
@@ -455,7 +458,8 @@ class rcmail extends rcube
 
         // add some basic labels to client
         $this->output->add_label('loading', 'servererror', 'connerror', 'requesttimedout',
-            'refreshing', 'windowopenerror', 'uploadingmany', 'close', 'save', 'cancel', 'alerttitle', 'confirmationtitle', 'delete', 'continue', 'ok');
+            'refreshing', 'windowopenerror', 'uploadingmany', 'close', 'save', 'cancel',
+            'alerttitle', 'confirmationtitle', 'delete', 'continue', 'ok');
 
         return $this->output;
     }
@@ -485,11 +489,6 @@ class rcmail extends rcube
         if (!$_SESSION['user_id']) {
             $_SESSION['temp'] = true;
         }
-
-        // restore skin selection after logout
-        if ($_SESSION['temp'] && !empty($_SESSION['skin'])) {
-            $this->config->set('skin', $_SESSION['skin']);
-        }
     }
 
     /**
@@ -774,8 +773,12 @@ class rcmail extends rcube
         $this->plugins->exec_hook('session_destroy');
 
         $this->session->kill();
-        $_SESSION = array('language' => $this->user->language, 'temp' => true, 'skin' => $this->config->get('skin'));
+        $_SESSION = array('language' => $this->user->language, 'temp' => true);
         $this->user->reset();
+
+        if ($this->config->get('skin') != $this->default_skin && method_exists($this->output, 'set_skin')) {
+            $this->output->set_skin($this->default_skin);
+        }
     }
 
     /**