fix(js-catcher): allow optional context and set statusCode on fetch fail

[Dobrunia]

Summary

Two small fixes in the JavaScript catcher:

1. Validation — optional context
   validateContext() was treating missing/undefined context as invalid and logging "Context must be an object". Context is optional in HawkInitialSettings and in setContext(context?: EventContext), so undefined should pass validation.
   Updated the check to only fail when context is present but not an object (context && !Sanitizer.isObject(context)), so undefined is accepted.
   

2. Breadcrumbs — fetch failure
   When a fetch request fails (e.g. network error), the breadcrumb in the catch block now explicitly sets statusCode: 0 in data, so the UI can consistently treat failed requests (e.g. for coloring).