According to the HTML specification:
> The default value is the minimum plus half the difference between the
> minimum and the maximum, unless the maximum is less than the minimum,
> in which case the default value is the minimum.
So for new progress bars, we had a numeric value of `nil` and a range
value of `50`, meaning the input fields weren't in sync.
Manually triggering the event on the progress, while not an ideal
solution (ideally we would be able to define `0` as default), sets the
value of the numeric field.
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