[5.6] Fixes for job queuing errors

[erupakov]

Platform: Lumen 5.6
When using scheduled jobs with queuing there is an error appear in log files:
Running scheduled command: App\Jobs\CheckIncomeJob

In Schedule.php line 99:

Call to a member function onQueue() on string
This patch fixes this error

[deleugpn]

I think there has been a back-and-forth about this change.

Edit: My bad. I've look at the history of this file and perhaps my memory is about somewhere else in the code.

Would be nice to have some tests about this, though. Few commits around this area without any tests already. #21820 and #21473.

[X-Coder264]

We also got #25216 on the 5.7 branch which includes tests 😄

[taylorotwell]

Need some example of how to recreate this.