Bash's 'nounset' yields 'ZSH_VERSION: unbound variable'

[LinuxOnTheDesktop]

I put the latest code of s.sh into a file.

I created this:

#!/usr/bin/env bash
set -o nounset
source "/my/path/h.sh" # replace with a real path
echo "abcdefghijklmnopqrstuvxywz" | h a b c d e f g h i j k l

Result: h.sh: line 59: ZSH_VERSION: unbound variable,