Watch Directory fires cast exception when retrying after error

Repro steps:
1. create a simple workflow like this
1. Watch-Directory (every trigger is good, eg on file created)
2. Wait fo 20 secs
3. Finish
2. run the workflow
3. stop the process during the "Wait" step

When the service starts again, we'll receive the following exception


Checking the code I think the problem is here:


probably it should be better with this:


If the fix is correct, I could open a quick PR.