(bug 40889) Follow-up 6f1d4db3: Fix the upload form when radio buttons are shown.

The previous change had broken the upload form if URL uploads or
some other possible upload source types are enabled - i.e. in
the case when there are radio buttons. The "incorrect" label ID
was used by radiobutton.

Change-Id: I7c15fd4250b6a2d26af2cc0373da5ac6c884d690