With set -u, bash 3.2 treats empty array expansion
"\${CTL_BOOTSTRAP_ARGS[@]}" as an unbound variable.
Use ${CTL_BOOTSTRAP_ARGS[@]+"..."} pattern to skip
expansion when the array is empty.
Replace [[ -v ${key} ]] (requires bash 4.2+) with
[[ -n "${!key+x}" ]] which works on bash 3.2+ and all
POSIX-compatible shells.
macOS ships with bash 3.2, causing:
./ctl.sh: line 42: conditional binary operator expected
Alan