live555: Fix fallback case for unsupported transport.
live555: Fix fallback case for unsupported transport.

This was broken by [175310ff6066991ee45e2a839f8c53e12b75e6d4] which introduced "forced mcast".

jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.1,krichter722/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,krichter722/vlc,xkfz007/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1