I created a report in Crystal Reports 2013 SP4 and the report runs correctly. The report is a Customer Search and utilizes several optional parameters, including one optional parameter for Salesperson, which is a dynamic parameter.
When trying to run the report in a VS application, the report crashes if you do not select a value for the Salesperson. I also noticed, that even when you do select a value, the parameter shows as blank when it is added as a field in the report output.
In CR2013, the report runs correctly, regardless of whether or not a Salesperson is supplied. When a Salesperson is supplied, it is properly displayed in the report output as well.