fix: Don’t fail on issues without linked PRs (#473)

This PR fixes the error—

> Unhandled error: TypeError: Cannot use 'in' operator to search for
'source' in undefined

—which has caused “Test” workflow run failures (e.g.
https://github.com/github-community-projects/continuous-ai-for-accessibility-scanner/actions/runs/17551616985).

This PR does 3 things:
1. Removes the use of `in` by replacing it with [optional
chaining](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining).
This moots the error above.
2. Adds support for multiple timeline item nodes, in case other timeline
items are added _before_ the scanner action assigns an issue to Copilot
(i.e. when Copilot coding agent’s PR isn’t the first item).
3. Logs when a linked PR is not found for an issue, to help with future
debugging.

Author: smockle

.github/workflows/test.yml

@@ -25,7 +25,7 @@ jobs:
     if: ${{ github.event_name != 'pull_request' || github.event.pull_request.draft == false }}
     strategy:
       matrix:
-        site: [ "sites/site-with-errors" ]
+        site: ["sites/site-with-errors"]
     steps:
       - name: Checkout
         uses: actions/checkout@v5
@@ -103,14 +103,12 @@ jobs:
               }`;
               const variables = { owner, repo, issueNumber: parseInt(issueNumber, 10) }
               const result = await github.graphql(query, variables)
-              let pullRequest;
-              if ('source' in result.repository?.issue?.timelineItems.nodes[0]) {
-                pullRequest = result.repository?.issue?.timelineItems.nodes[0].source;
-              } else if ('subject' in result.repository?.issue?.timelineItems.nodes[0]) {
-                pullRequest = result.repository?.issue?.timelineItems.nodes[0].subject;
-              }
-              if (pullRequest) {
-                finding.pullRequestUrl = pullRequest.url;
+              const timelineNodes = result?.repository?.issue?.timelineItems?.nodes || [];
+              const pullRequestNode = timelineNodes.find(n => n?.source?.url || n?.subject?.url);
+              if (pullRequestNode) {
+                finding.pullRequestUrl = pullRequestNode.source?.url || pullRequestNode.subject?.url;
+              } else {
+                core.info(`No pull request found for issue: ${finding.issueUrl}`);
               }
             }
             fs.writeFileSync(process.env.FINDINGS_PATH, JSON.stringify(findings));