[Symfony][Minor] profiler view when no messages collected during the request

[dkarlovi]

This is really super-minor, but no reason not to fix it as the fix is super-minor as well. :)

In Symfony profiler, Enqueue will output a header-only table if no messages were sent during the request. What all other profiler views do in this situation is something like this:

<div class="empty">
    <p>No queries were performed.</p>
</div>

[makasim]

Could you please do a PR?

[dkarlovi]

Sure.