crc32_iscsi_00 deal with null buffer

In the distributed storage system Ceph(github.com/ceph/ceph), it needs to deal with the case when the input buffer is NULL while the length isn't zero: https://github.com/ceph/ceph/blob/master/src/test/common/test_crc32c.cc#L358
On IA platform, the crc32 is implemented by:
1. https://github.com/ceph/ceph/blob/master/src/common/crc32c_intel_fast_asm.s
This file is copied from : https://github.com/intel/isa-l/blob/master/crc/crc32_iscsi_00.asm
2. https://github.com/ceph/ceph/blob/master/src/common/crc32c_intel_fast_zero_asm.s
This file changes something from crc32c_intel_fast_asm.s to be renamed as crc32c_intel_fast_zero_asm.s to deal with the case when the input buffer is NULL.

Could isa-l adds support to deal with NULL buffer input crc32c case?