A change in e28a595b52 introduced an issue where the "Share camera as
content" modal always has it's "share" action flagged as disabled. This
is due to a short-circuit introduced in the initial gUM procedure that
does not clear the "disabled" state before exiting.
Properly reset the "disabled" sharing state after the initial gUM in
video-preview when "Share camera as content" is used, thus fixing the
aforementioned issue.