r129 of liblz4 enabled sparse file support by default; this breaks  lz4c decompression when used in a pipeline. For example, <some compressed lz4 stream> | lz4c -d | <some other tool> isn't working now, but worked in r128.
I would suggest either reverting back to r128 for now, or applying the changes made to the current dev branch  which gracefully recovers rather than errors out.
A commit references this bug:
Date: Sun May 24 18:01:05 UTC 2015
New revision: 387288
Fix decompression in a pipeline: import fix from dev branch in
Submitted by: eborisch+FreeBSD@gmail.com
Approved by: adamw (maintainer, implicit)
Tested with the example command line from
on 10.1 and 9.3.