On line 3,

  if [ -n "${sopsCreateGPGHome}" ]; then

uses sopsCreateGPGHome, which may be unbound (unless the user has set it). Since this file gets sourced into shells, it can break when it’s sourced into a shell with nounset (set -u) enabled (which I have just run into).

This should either also check that the variable is bound

  if [ -v sopsCreateGPGHome && -n "${sopsCreateGPGHome}" ]; then

or should bind it preemptively

sopsCreateGPGHome=
…
  if [ -n "${sopsCreateGPGHome}" ]; then