Improve error logging in pin-bundle-images.sh for EMPTY_SHA

Add detailed error output when SHA cannot be found for a bundle image.
This helps debug issues like local path replacements being processed
as bundles.

Error output now includes:
- MOD_PATH: The go module path being processed
- BASE: The extracted operator base name
- REF: The git reference/version
- REPO_URL: The repository URL being queried
- REPO_CURL_URL: The API URL used for queries
- Bundle: The full bundle image reference attempted

Example output when failing:
  ERROR: Failed to find bundle image SHA for:
    MOD_PATH: ./api
    BASE: api
    REF: 00010101000000-000000000000
    REPO_URL: quay.io/openstack-k8s-operators
    REPO_CURL_URL: https://quay.io/api/v1/repository/./api
    Bundle: quay.io/openstack-k8s-operators/api-operator-bundle:...

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Martin Schuppert <mschuppert@redhat.com>

Author: stuggi

hack/pin-bundle-images.sh

@@ -104,6 +104,13 @@ for MOD_PATH in ${MOD_PATHS}; do
     fi
 
     if [ -z "$SHA" ]; then
+        echo "ERROR: Failed to find bundle image SHA for:"
+        echo "  MOD_PATH: $MOD_PATH"
+        echo "  BASE: $BASE"
+        echo "  REF: $REF"
+        echo "  REPO_URL: $REPO_URL"
+        echo "  REPO_CURL_URL: $REPO_CURL_URL"
+        echo "  Bundle: ${REPO_URL}/${BASE}-operator-bundle:$REF"
         echo ",EMPTY_SHA:$REF:$REPO_CURL_URL"
         exit 1
     fi