Only write QA_ISSUE_URL when QA issue exists
A QA issue doesn't always get created.
Fixes https://sentry.gitlab.net/gitlab/release-tools/issues/2379756/
See https://ops.gitlab.net/gitlab-org/release/tools/-/jobs/2381070
A QA issue doesn't always get created.
Fixes https://sentry.gitlab.net/gitlab/release-tools/issues/2379756/
See https://ops.gitlab.net/gitlab-org/release/tools/-/jobs/2381070