Custom default channel setting via ini prevents configurability of new virtual servers

[Kissaki]

When a channelid > 0 is set as default channel id via murmur.ini,
https://github.com/Kissaki/MumPI/blob/master/classes/MurmurClasses.php#L162
throws an exception, resulting in the config subpage stopping to load, rendering it unusable.

<ThatOtherGuy_> Default Channel  Fatal error: Uncaught exception ::Murmur::InvalidChannelException { } thrown in /home/nullcorp/public_html/MumPI/classes/MurmurClasses.php on line 164

Add a catch for that exception, and/or defaulting to default-chanid 0.
Setting it to 0 for a new vserver would be good as well, in MumPI, or better yet in Mumble itself.