Merge pull request HangfireIO#469 from mkravchuk7/master

Prevent infinite loops when trying to change state of a job that doesn't exist

Author: odinserj

src/Hangfire.Core/States/BackgroundJobStateChanger.cs

@@ -132,7 +132,8 @@ private static JobData GetJobData(StateChangeContext context)
                     return jobData;
                 }
 
-                if (context.CancellationToken.IsCancellationRequested)
+                if (context.CancellationToken.IsCancellationRequested ||
+                    context.CancellationToken == CancellationToken.None)
                 {
                     return null;
                 }