Notice: Undefined index: description in advagg_admin_settings_form() (line 177 of /advagg/advagg.admin.inc)

Fix:

  $form['advagg_async_generation'] = array(
    '#type'           => 'checkbox',
    '#title'          => t('Generate CSS/JS files on request (async mode)'),
    '#default_value'  => variable_get('advagg_async_generation', ADVAGG_ASYNC_GENERATION),
    '#disabled'       => $ret['advagg_async_generation']['severity'] == REQUIREMENT_ERROR ? TRUE : FALSE,
-    '#description'    => t('Current State: !value', array('!value' => filter_xss($ret['advagg_async_generation']['value'] . ' ' . !empty($ret['advagg_async_generation']['description']) ? $ret['advagg_async_generation']['description'] : ''))),

+    '#description'    => t('Current State: !value', array('!value' => filter_xss($ret['advagg_async_generation']['value'] . ' ' . (!empty($ret['advagg_async_generation']['description']) ? $ret['advagg_async_generation']['description'] : '')))),

  );