Hi,
When being executed, the File Move action publishes a variable called 'FILE_NB', which indicates the number of files treated.
You can use the value of this variable to design the flow after your action, to separate the execution into two branch, for instance:
You can replace the Empty actions here by any action.
You could send a mail, generate an error through scripting, ...
This article demonstrates how to generate an error:
stambia.org/doc/80-development-hints-and...s-to-end-with-errors
Is this what you wanted to achieve ?