Download is stuck when choosing XAR as output and leaving the Target field empty

Steps to reproduce:

1. Install the WikiStream Application and the WikiStream Confluence XML module (both v5.4.3)
2. Go to WikiStream.WebHome and pick "Confluence XML import stream (confluence+xml)" for the Input Type and "XAR output stream (xwiki+xar/1.1)" for the Output Type
3. Type in the source of your zip in this format:

   file:D:\xwiki\confluence.zip

   in the source field from the "INPUT CONFIGURATION"

4. Click Convert

The download starts for a file named "target.htm", but it gets stuck forever on both Chrome and Firefox. I've attached the zip file I used for testing.