Fix UIP bug found in passing
Fix UIP bug found in passing

Somehow on Firefox it is possible to forget all page data but still
have the sequence pull-down pre-populate with the most recently used
value. I know not how. When this happens, the script breaks and the
page won’t do anything.

Catch this scenario and reset the pull-down.

bbc/ebu-tt-live-toolkit,ebu/ebu-tt-live-toolkit,bbc/ebu-tt-live-toolkit,bbc/ebu-tt-live-toolkit,ebu/ebu-tt-live-toolkit,ebu/ebu-tt-live-toolkit