added empty $template_config_groups var

for template changes, if previous template had these set

templates/2k11/config.inc.php

@@ -93,6 +93,7 @@ $template_config = array(
     )
 );
 
+$template_config_groups = NULL;
 $template_global_config = array('navigation' => true);
 $template_loaded_config = serendipity_loadThemeOptions($template_config, $serendipity['smarty_vars']['template_option'], true);
 serendipity_loadGlobalThemeOptions($template_config, $template_loaded_config, $template_global_config);