How to check whether an optional FeatureSet parameter was set by the user in a geoprocessing script tool?

I have created a custom geoprocessing script tool which contains an optional FeatureSet parameter.

When unpacking the parameters in the script, the FeatureSet is defined as a RecordSet object, even though no input was received. It seems to set a default value if it was not entered.

I need to check if this parameter was specified by the user or not.

For example, when I run this through ArcMap without a FeatureSet parameter the following occurs:

exportAOI = arcpy.GetParameter(3)
arcpy.AddMessage('AOI is: ' + str(exportAOI))
# AOI is: <geoprocessing record set object object at 0x14133578>

I was expecting exportAOI to be None.

How can I determine whether the user actually set this type of parameter?