[chore] Do not fail if JSON is not found in previous issue (open-tele…

…metry#33395)

**Description:**

Avoid crashing when JSON section is not present in previous ISSUE

**Link to tracking Issue:**

open-telemetry#33388 

**Testing:**
```
act -j get_issues  -e <(echo '{"repository": {"owner": {"login": "your-github-username"}}}') -s GITHUB_TOKEN=<your-token>
```

.github/workflows/scripts/generate-weekly-report.js

@@ -285,7 +285,8 @@ function parseJsonFromText(text) {
     // Parse the found string to JSON
     return JSON.parse(match[1]);
   } else {
-    throw new Error("JSON data not found");
+    debug({msg: "No JSON found in previous issue"})
+    return null
   }
 }