Fix similarIssues.yml to not fail when no similar issues found (#16542)

Added an if statement to similarIssues.yml so that the logic can be
updated to not show as 'failure' when no similar issue is found.

Related: craigloewen-msft/GitGudSimilarIssues#33

.github/workflows/similarIssues.yml

@@ -21,6 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       issues: write
+    if: needs.getSimilarIssues.outputs.message != ''
     steps:
       - name: Add comment
         run: gh issue comment "$NUMBER" --repo "$REPO" --body "$BODY"