Symfony version(s) affected: 4.2.2

Description
A couple of images should explain the problem.
This is profiler I see:

Then, I click on Twig icon and I get this:

So, the Twig icon is active (e.g. not in gray) even when profiled request rendered no templates.
This is inconsistent with other profiler icons, that are grey when no info is collected and active otherwise.

How to reproduce
Just call a route in your application when Twig is not involved, e.g. an action returning a JsonResponse.

Possible Solution
Likely some check is missing.