ci: disable benchmark results comment if there's no diff (#8515)

.github/workflows/perf_emulation_handle_results.yml

@@ -116,6 +116,10 @@ jobs:
             }
 
             const commentBody = fs.readFileSync(commentPath, 'utf8').trim();
+            if (commentBody.length == 0) {
+              console.log("Not generating a comment as the comment body is empty");
+              process.exit(0);
+            }
             const prNumber = Number(fs.readFileSync(prPath, 'utf8').trim());
 
             github.rest.issues.createComment({