fc-cache segfaults within FcDirScan() because FcDirScan()
if (FcDirCacheReadDir (set, dirs, dir))
FcGlobalCacheReferenceSubdir (cache, dir);
But cache can be NULL. Adding a if (cache) before
calling ReferenceSubdir() looks right and tests to fix
Probably can be made a lot more minimal, but the fix was obvious
Oops. Forgot to commit the fix for this...