check encoding of attached files and convert to utf-8

locallib.php

@@ -294,17 +294,16 @@ function get_text_content_from_file($usercontext, $draftareaid, $keepfilename, $
     // TODO: make sure the mimetype is plain text
     // even task.xmls may contain mistakes (eg PDF )
 
-    //check if encoding of attached ist utf-8 else convert
+    //check if encoding of attached file is utf-8 else convert
     $content = $file->get_content();
-    if($encoding!==false){
+    if($encoding!=null){
         $enc=$encoding;
     } else {
-        $enc = mb_detect_encoding($content, mb_detect_order(), true);
+        $enc = mb_detect_encoding($content, null, true);
         if($enc===false){
             throw new invalid_parameter_exception('Encoding of attached file ' . $filepath . $filename . 'could\'nt be detectet.');
         }
     }
-    $content = mb_convert_encoding($content, $enc, 'UTF-8');
     if($enc!=='UTF-8'){
         $content = mb_convert_encoding($content, 'UTF-8', $enc);        
     }