Resolved crash when cancelling an in-progress episode download

[ribbons]

When an episode download is cancelled using the toolbar button, the application crashes with the following exception in the download thread:

System.NullReferenceException: Object reference not set to an instance of an object.
   at RadioDld.DownloadHandler.DownloadProgThread() in E:\Development\Radio Downloader\Classes\DownloadHandler.cs:line 250
   at System.Threading.ExecutionContext.runTryCode(Object userData)
   at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

This is affecting multiple users and I can easily reproduce it.