Symfony version(s) affected: 4.0.9/4.1.0-BETA1

Description
Commit 4e527aa added a service http_exception_listener. This registers a system-wide exception handler that sets request's _controller attribute to a closure during kernel.exception.
Also this closure controller generates a response on the event. As a consequence of that, this triggers listeners on kernel.response event - with _controller as a closure instead of previously not being invoked at all, and the generated response instead of null.

How to reproduce
Failing test case provided separately in #27213.

Additional context
Encountered in API-only application, no templating etc., only custom request/response handling and custom exception handling.