ListDirectory returns error on empty directory

[wangkuiyi]

When a directory is empty, C.hdfsListDirectory returns nil, and the condition at L391 of hdfs.go would judge the call to hdfs.ListDirectory had failed.

Could we have a more accurate judge about the fail of C.hdfsListDirectory?

[zyxar]

I guess I have encountered this issue before, however the error condition or return value cannot be determined simply. I think I would inspect it later.