In the font in question, there are a couple of `topDict` entries that have invalid values (`0xF 0xF`, i.e. just eof markers without any actual numbers).
This causes the `parseFloatOperand` function, inside `CFFParser_parseDict`, to return `NaN`. Currently we pass this broken font onto the browser, which OTS unsurprisingly rejects.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1068432.
Re: issue 7261.
Given the we have `gulp fonttest`, which tests the `fonts.js` functionality at a higher level, and that we have *a lot* of font specific reference tests, I'm not convinced that we *also* need unit-tests for it.
