When uploading files using multi-part encoding, parameter count from request.getParameterMap() and request.getParameterNames() are different.

It seems both methods attempt to filter out FileItem parameters, but the getParameterMap includes the parameter with an empty values list in the returned map.

Steps to reproduce:

1. deploy attached reproducer
2. go to http://localhost:8080/reproducer
3. upload file
   Expected:

   Parameter Map size: 1
   Parameter Names count: 1
   

   Actual:

   Parameter Map size: 2
   Parameter Names count: 1