Move SetDefaultTLSConfig before register(cfg) in loader.go so
ParseService can access it when building handlers. Also add a
defensive nil check in socks5 serverSelector.Select() for
MethodTLS to prevent future ordering regressions.
Root cause: in selector.go, Select() tried to read ClientHello
via TLSConfig.GetConfigForClient but s.TLSConfig was nil because
register(cfg) -> ParseService -> handler Init ran before
SetDefaultTLSConfig was called from loader.go.
ginuerzh