Upload file modal does not update state after files selected

[flongford]

Currently the UX when uploading files is diminished by the upload modal not refreshing state properly once a file is selected.

Consequently, the "Upload" button will remain disabled and the upload cannot be performed. The upload can be completed if another file is selected in the modal, however.

I'm not sure why this is occurring, since I'm unable to find any error traceback. The only message that may be of significance when running the container is:

Missing chrome or resource URL: resource://gre/modules/UpdateListener.jsm