[XeTeX] Another fontspec bug

[Ian-Mathew Hornburg]

There might be a metadata in the font containing text specifying which
languages the font supports, but that is different from there being a
language *feature* in the font.

Oftentimes, a font will support a given script (say, Malayalam), but
have no OpenType language tags in the font. This doesn’t necessarily
mean an omission on the part of the font designer, but rather that
there is no language-specific functionality needed for the Malayalam
script.

By specifying a language with fontspec, it’s likely attempting to
activate an OpenType feature that the font doesn’t contain. Try it
again, omitting the language setting in fontspec.