Silent woff2_decompress failure?

I'm having a very large font (that I cannot share publicly), that successfully compresses with woff2_compress:

```
Processing /path/to/my/font.ttf => /path/to/my/font.woff2
Compressed 45975079 to 21308821.
```

If I decompress it with fonttools, the result is fine (identical except for the head table, the mod date differs probably).

But `woff2_decompress` doesn't produce any output, and no error message is shown. The exit code is 1, though.

opentype-sanitizer is complaining about this file, too:
```
$ python -m ots /path/to/my/font.woff2
ERROR: Failed to convert WOFF 2.0 font to SFNT
Failed to sanitize file!
```
Perhaps it is the same issue, as it appears that ots uses `google/woff2`.

If anyone would be willing to have a look, I'd gladly share the file privately. It's from the GS CJK project, in case you're familiar with that.