job-completed notification is not delivered for a printer subscription when the job is canceled

[m7913d]

Describe the bug
The job-completed notification is not delivered to a printer subscription when the job is canceled.
Currently, this event is only delivered for job subscription or whole server subscriptions.

To Reproduce
Steps to reproduce the behavior:

1. Create a printer subscription for at least the job-completed event
2. Pause the printer (to be able to cancel the job)
3. Print a document to the printer
4. Cancel the job

Expected behavior
A job-completed notification should be send for the printer subscription.

Possible solution
This issue is caused by job->printer only being set when the job actually starts printing. Hence, when cupsdSetJobState is called for the canceled job, a null pointer is passed to cupsdAddEvent for the dest argument.

It may be solved by adding the following lines to the cupsAddEvent function:

if (!dest && job && job->dest)
  dest = cupsdFindDest(job->dest); // lookup the printer if it is not explicitly provided and the job contains a named destination

System Information:
All OSes / cups versions

[michaelrsweet]

"job->dest" cannot be NULL, so we can simplify the change a little:

[master 761272c] Fix job-completed event notifications for jobs that are canceled before they are started (Issue #1209)

[2.4.x d516661] Fix job-completed event notifications for jobs that are canceled before they are started (Issue #1209)