Issue #2659746 by gisle: Do not choke on invalid multibyte sequences

advanced_help.module

@@ -640,7 +640,11 @@ function advanced_help_view_topic($module, $topic, $popup = FALSE) {
     $info = advanced_help_get_topic($module, $topic);
     $file = "./$file_info[path]/$file_info[file]";
 
+    // Fix invalid byte sequences (Issue #1330056).
     $output = file_get_contents($file);
+    mb_substitute_character(0xfffd);
+    $output = mb_convert_encoding($output, 'UTF-8', 'UTF-8');
+
     if (isset($info['readme file']) && $info['readme file']) {
       $ext = pathinfo($file, PATHINFO_EXTENSION);
       if ('md' == $ext && module_exists('markdown')) {