QHttpServer crashes when lambda catches `this`

I encountered a problem when using QtHttpServer. If lambda (registered for a route) catches `this`, program ends in undefined behavior. Example to show how to reproduce this:

class A
{
  QtHttpServer server;
  int data;
  A() 
  {
    server.route("/", [this]()
    {
      qDebug() << data;
    });
    server.listen(QHostAddress::Any);
  }
}

This happens, because arguments of function route are perfectly forwarded deeper. Then in routeImpl the lambda is caught by reference when creating a rule. The problem is, the temporary lambda created in above example stops existing as soon as line server.route(...); ends. As a result we end up with a dangling reference in Rule object. It still works for cases where our lambda doesn't rely on accessing external variables (see example here: https://rextester.com/HGDT10316 ), but it still isn't something that should be done.

For my project where I'm using QtHttpServer I used following workaround: when creating new Rule in routeImpl I don't capture viewHandler by reference, but by value. This way I can be sure that the lambda was copied and won't be deleted prematurely.