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, ...
The Get Files with FTP action is also publishing the number of files treated in a 'FILE_NB' session variable.
You can so implement a similar logic on this action without any problem.
More generally, all the variables available in the Process can be used in a link condition.
If needed, you can see all the variables published by an action after its execution in the 'Variable' View in the Designer.