Checking if we have headers (#2).

extended-toc.php

@@ -433,6 +433,10 @@ if( !class_exists('ExToC') ) {
     private function exctract_headings($pagenum) {
       /** find all header tags within the page **/
       preg_match_all('/(<h([1-6]{1})[^>]*>).*<\/h\2>/msuU', $this->pages[$pagenum-1], $matches, PREG_SET_ORDER);
+      
+      if (count($matches) == 0) {
+          return null;
+      }
 
 			/** Check the headings that are desired */
 			if( count($this->options['heading_levels']) != 6 ) {