fix: handle unbound variable for stable parameter in verify_public_ecr and verify_dockerhub

[TheanLim]

Summary

publish.sh runs with set -euo pipefail. The -u flag causes bash to treat any reference to an unset variable as an error and immediately exit the script.

verify_public_ecr and verify_dockerhub both assigned their first positional parameter with stable=${1}. When either function is called without an argument, $1 is unset and bash aborts the script with unbound variable before the verification logic runs.

Changed stable=${1} to stable=${1:-} in both functions. The :- default value syntax tells bash to use an empty string if $1 is unset, satisfying -u without changing behavior when the argument is provided.

Testing

A snippet to test the behavior

#!/bin/bash
set -euo pipefail

echo "=== BEFORE fix: stable=\${1} ==="
( set -euo pipefail; stable=${1}; echo "stable=${stable}" ) && echo "OK" || echo "FAILED: unbound variable"

echo ""
echo "=== AFTER fix: stable=\${1:-} ==="
( set -euo pipefail; stable=${1:-}; echo "stable=${stable}" ) && echo "OK: stable is empty string, no error"

Output:

./snippet.sh            
=== BEFORE fix: stable=${1} ===
./test.sh: line 5: 1: unbound variable
FAILED: unbound variable

=== AFTER fix: stable=${1:-} ===
stable=
OK: stable is empty string, no error

Description for the changelog

fix: handle unbound variable for stable parameter in verify_public_ecr and verify_dockerhub

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.