Reliably determine id from url about soundboard

[villermen]

Workaround in 6f4fec1. This will make sure that even if no argument is given, the one JavaScript ends up with will not throw an error but silently discard it somewhere along the road.

[villermen]

Once we have a base url in place we can probably figure this one out pretty easily using some clever JavaScript parsing.

[villermen]

So. The base tag needs to be set using a config option, but the config options are loaded relatively by a script relative to the index. Setting the base url looks like an impossible feedback loop.