benchmark mode claims a decompression error on this data w/huf

```
% ./fse -h -b ./xxx
FSE : Finite State Entropy, 64-bits demo by Yann Collet (Jul 17 2020)
!! Error decompressing block 4 of cSize 18041 !! => (Corrupted block detected)
```

gunzip the below file and run the above.
[xxx.gz](https://github.com/Cyan4973/FiniteStateEntropy/files/4940374/xxx.gz)
The 'xxx' file appears to survive a huf compress and then a huf decompress intact when doing them individually, so perhaps this is an issue specific to the benchmark mode.

Tested with 3865a704e8079fb45fc921480a6c351bb6bfbd72