Fix hypothetical NULL dereference on stream open.
Fix hypothetical NULL dereference on stream open.

clang --analyze pointed out that, technically, 'uri' can be NULL here.
This would mean that the server sending us a stream open without a
namespace would crash us!

So, we use wocky_strdiff rather than strcmp.

freedesktop-unofficial-mirror/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky