GemistDownloader voor Mac

[henzan]

Ik gebruik al jaren gemistdowloader op een windows PC. Na installatie van gemistdownloader op mijn mac (OS Sierra) worden de gekozen bestanden bij NPO.nl niet gedownload. Ik krijg de volgende foutmelding:
Unhandled Exception:
System.ArgumentNullException: Value cannot be null.
Parameter name: uriString
  at System.Uri..ctor (System.String uriString, System.UriKind uriKind) [0x0000c] in <5071a6e4a4564e19a2eda0f53e42f9bd>:0 
  at System.UriBuilder..ctor (System.String uri) [0x0006c] in <5071a6e4a4564e19a2eda0f53e42f9bd>:0 
  at GemistDownloader.Downloader.Create (System.String PlainURL, GemistDownloader.DownloadDetails ItemDetails, System.String OutputFile, GemistDownloader.Downloader+DownloadType type, GemistDownloader.Controller.Core+VideoType VideoType, System.Boolean OverrideFileName, GemistDownloader.DownloadSettings DownloadSettings) [0x0000b] in <da4e5c960a5042bcaf23a4d99589317a>:0 
  at MainWindow+<DownloadButtonClick>d__25.MoveNext () [0x00233] in <da4e5c960a5042bcaf23a4d99589317a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__1 (System.Object state) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context (System.Object state) [0x0000e] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x0008d] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem () [0x0002a] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading.ThreadPoolWorkQueue.Dispatch () [0x00096] in <8f2c484307284b51944a1a13a14c0266>:0 
  at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.
Deleting expired sessions...24 completed.

[Proces voltooid]
Hoe kan ik dit oplossen?