Bitrate information is sometimes "0"

[haecker-felix]

On some stations the bitrate information is 0.

For example "Deutschlandfunk"

id":"59591"
"name":"Deutschlandfunk  [Ogg 104k]",
...
"bitrate":"0"
...

When the bitrate information can't be read correctly, it think it's better to use "-" or "?" instead of 0.