zero block while unpacking ckeditor_3.4.tar.gz

I downloaded ckeditor_3.4.tar.gz, but when I try to unpack it, I get this message:

# tar -xzf ckeditor_3.4.tar.gz
tar: A lone zero block at 11720
(tar version is 1.23)

What does it mean? Do I have to make worry about it?