Fix a NullPointerException when there are no test results.

If there are no test results (e.g. if the build fails before the tests run)
then build.getAction(AbstractTestResultAction.class) returns null.
Add a check for this case.
Add job URL to the Jira ticket.

Add the URL for the job that caused the test failure to the Jira ticket.
Merge branch 'fix-crash-missing-tests'
Merge branch 'add-job-url'