Contribution Thank-you Letters grouped by contact - option to send email when possible + print PDF for all is broken

If you enable PDF Attachments in system settings, and select "Send emails with an attached PDF where possible. Generate printable PDFs for all " - the printable PDF's generated are completely EMPTY (see attached CiviLetter-17.pdf). After clicking 'Done' I get these Notices:

Notice: Undefined index: in Cpdf->getFontHeight() (line 3098 of /Users/dgg/git/crm_v4.5/packages/dompdf/lib/class.pdf.php).
Notice: Undefined index: in Cpdf->getFontHeight() (line 3098 of /Users/dgg/git/crm_v4.5/packages/dompdf/lib/class.pdf.php).
Notice: Undefined index: in Cpdf->getFontHeight() (line 3098 of /Users/dgg/git/crm_v4.5/packages/dompdf/lib/class.pdf.php).
Notice: Undefined index: in Cpdf->addText() (line 3649 of /Users/dgg/git/crm_v4.5/packages/dompdf/lib/class.pdf.php).
Notice: Undefined index: in Text_Renderer->render() (line 93 of /Users/dgg/git/crm_v4.5/packages/dompdf/include/text_renderer.cls.php).