Notice: Undefined index: exclude_empty

I get always the next notice when i submit a webform
When 'Generate PDF Document' is enabled and the E-mail settings 'Attach PDF as an attachement to the e-mails sent to the form recipients' is also enabled.

Notice: Undefined index: exclude_empty in webform_submission_render() (regel 641 van /var/www/sites/all/modules/contrib/webform/includes/webform.submissions.inc).
Notice: Undefined index: exclude_empty in webform_submission_render() (regel 641 van /var/www/sites/all/modules/contrib/webform/includes/webform.submissions.inc).

It's look like a problem of webform, but it occures only when i play with the 'Attach PDF ....' option.

Any idea's ? Any one else with tesame problem ?