Dart null / false / empty checking: How to write this shorter?

This is my code for true on everything but empty string, null and false:

if (routeinfo["no_route"] == "" || routeinfo["no_route"] == null || routeinfo["no_route"] != false) {
    // do sth ...
}

This is my code for true on everything but empty string, null, false or zero:

if (routeinfo["no_route"] == "" || routeinfo["no_route"] == null || routeinfo["no_route"] != false || routeinfo["no_route"] == 0) {
    // do sth...
}

How can I write this shorter in Dart? Or is it not possible?