Fix reference to non-existing class rcube_output_html (#1488948)

plugins/newmail_notifier/newmail_notifier.php

@@ -51,7 +51,7 @@ class newmail_notifier extends rcube_plugin
         else { // if ($this->rc->task == 'mail') {
             $this->add_hook('new_messages', array($this, 'notify'));
             // add script when not in ajax and not in frame
-            if (is_a($this->rc->output, 'rcube_output_html') && empty($_REQUEST['_framed'])) {
+            if ($this->rc->output->type == 'html' && empty($_REQUEST['_framed'])) {
                 $this->add_texts('localization/');
                 $this->rc->output->add_label('newmail_notifier.title', 'newmail_notifier.body');
                 $this->include_script('newmail_notifier.js');

program/include/rcmail_output_html.php

@@ -668,7 +668,7 @@ class rcmail_output_html extends rcmail_output
      *
      * @param  string $input
      * @return string
-     * @uses   rcube_output_html::parse_xml()
+     * @uses   rcmail_output_html::parse_xml()
      * @since  0.1-rc1
      */
     public function just_parse($input)