[5.0] Return a response object for routeMiddleware

[etcinit]

While I was trying to get the VerifyCsrfToken middleware to work optionally using $routeMiddleware, I noticed that middleware declared in $routeMiddleware instead of $middleware does not get a response object when $next($response) is called (at least not every time), instead it gets whatever the controller or route handler returned (a View object in most cases).

The proposed change below makes sure the response is prepared before it goes back through the route middleware pipeline

Also, some spaces to tabs conversion

[GrahamCampbell]

Please don't change all the indentation.

[taylorotwell]

Hmm, this might should be considered more of a bug, and thus should go into 5.0 branch.

[etcinit]

Ok, reapplied the commits to 5.0. New PR #7454