RouteParser is not always present

[l0gicgate]

When the RoutingMiddleware is automatically instantiated by the RouteRunner because routing was not performed:
https://github.com/slimphp/Slim/blob/4.x/Slim/Routing/RouteRunner.php#L72

It calls performRouting but that means it doesn't append the RouteParser via this call since process is never called:
https://github.com/slimphp/Slim/blob/4.x/Slim/Middleware/RoutingMiddleware.php#L58

We need to fix this by moving that line into the performRouting method.

[l0gicgate]

@adriansuter I tried reaching out to you via Slack but it doesn't look like you've been active. Is there a way for me to direct message you somewhere else? I have something to ask you.