File/image uploading field doesn't work

Problem/Motivation

I recently upgraded from the stable branch to the development branch (6.2.0-rc3). Upon testing file uploads inside a webform I found that they did not work anymore. It would continuously say "File upload in progress." in an alert.

Steps to reproduce

1. Install 6.2.0-rc3 Webform module
2. Make a webform with a file upload field
3. Attempt to upload a file on the webform.
4. Press submit

EDIT:
A module I had installed broke this, not the webform module itself.