devongovett/pdfkit — pull request #303 by ef4 (2014-09-11 23:35:15+00:00)
Title: Prevent missing ascender from breaking layout

ZapfDingbats (and perhaps others) has no ascender or descender attributes. pdfkit is treating them as `NaN`, which causes `document.y` to also ends up as `NaN` if you try to render any text in this font.