Sending content based mimemails

I recognized a problem with sending content based mails from my own developed module. In the mimemail.inc (line 182):.
Error Message:
warning: realpath() expects parameter 1 to be a valid path, string given in C:\xampp\htdocs\eueco\sites\all\modules\mimemail\mimemail.inc on line 182.
$not_in_public_path = strpos(realpath($file), $public_path) === FALSE;
The line should be replaced with
if (@is_file($file)) $not_in_public_path = strpos(realpath($file), $public_path) === FALSE;
because if $content is filled really with $content, $file is equal to $content and this means, that $file is no path.