[PATCH] dwrite: Do not segfault if typographic features tag table is empty.

[Nikolay Sivov]

I think it's better to return earlier than fixing up counter, right
after second opentype_get_typographic_features().

Also please adjust patch subject, features are filtered using
script/locale arguments and default entries in the font, when available.
So it's normal for this method to occasionally return 0, even though
GSUB/GPOS is present.