Issue "can't cast empty string to a number value" 

I encounter this exception when running this code:

<cfquery name="myQuery" datasource="#datasource#">
    select * from myTable
</cfquery>

<jr:jasperreport jrxml="#datapath#/sample-001.jrxml" query="#myQuery#" xportfile="#workpath#/sample-001.pdf" exporttype="pdf"/>