Invalid data '' for CFSQLTYPE CF_SQL_INTEGER

Every time I enter data, I get this error report:

Invalid data '' for CFSQLTYPE CF_SQL_INTEGER

It might be related to this problem:

<cfloop collection="#cities#" item="cityID">

  products["#cityID#"] = [<cfset first = true><cfloop collection="#cities[cityID].products#" item="productID"><cfif first><cfset first = false><cfelse>,</cfif>{value:"#productID#", text:"#cities[cityID].products[productID]#"}</cfloop>];

  </cfloop>

There is a syntax error I cannot find in the line starting with product[

Can anyone help?

Thanks,