Is there any option to make the output 'null' to empty?

[liangkarl]

I love this simple tool, but I found out a problem here.
In shell script, the null value matches the string check inconvenient since [ -z $var ] is usually for checking empty string and the null string makes it failed. The solution here is that we need to remove the null string becoming a empty string.
I think maybe jp could add a option to solve this problem as it's really common for writing shell script.
Thanks!