Don't throw an error if flushing the output buffer fails. Closes blueimp#3201

Author: blueimp

server/php/UploadHandler.php

@@ -1078,8 +1078,8 @@ protected function readfile($file_path) {
             $handle = fopen($file_path, 'rb');
             while (!feof($handle)) {
                 echo fread($handle, $chunk_size);
-                ob_flush();
-                flush();
+                @ob_flush();
+                @flush();
             }
             fclose($handle);
             return $file_size;