MDL-19756 Fixed typo in debugging messages and added default string for close_window_button

lib/deprecatedlib.php

@@ -3528,7 +3528,7 @@ function update_module_button($cmid, $ignored, $string) {
  * @deprecated since Moodle 2.0
  */
 function update_categories_search_button($search,$page,$perpage) {
-    throw new coding_exception('update_tag_button() has been completely deprecated.');
+    throw new coding_exception('update_categories_search_button() has been completely deprecated.');
 }
 
 /**

lib/outputlib.php

@@ -2892,6 +2892,9 @@ class moodle_core_renderer extends moodle_renderer_base {
      * @return string|void if $return is true, void otherwise
      */
     public function close_window_button($text) {
+        if (empty($text)) {
+            $text = get_string('closewindow');
+        }
         $closeform = new html_form();
         $closeform->url = '#';
         $closeform->button->text = $text;