It's possible for the YouTube api to return zero broadcasts
or broadcasts without any streams--streams are what are
associated with stream keys. In this case, instead of showing
an empty selector or no selector, show a message with a link
to where the stream key can be obtained.

Provide a client-side notice if the YouTube live stream key
looks like it might be in the wrong format. Normally the
stream key looks like 4 groups of 4 numbers and letters,
each separated by a dash. The warning does not block submission
in case YouTube changes their stream key format.