panic了一次，udp

[blake-git]

May 8 22:28:50 blake shadowsocks-go: panic: runtime error: slice bounds out of range
May 8 22:28:50 blake shadowsocks-go: goroutine 549731 [running]:
May 8 22:28:50 blake shadowsocks-go: github.com/shadowsocks/shadowsocks-go/shadowsocks.handleUDPConnection(0xc42005e080, 0x11, 0x5a79e0, 0xc4200d8000, 0xc4204d4000, 0x100c, 0x100c, 0xc42005e0c0)
May 8 22:28:50 blake shadowsocks-go: /usr/local/go/src/github.com/shadowsocks/shadowsocks-go/shadowsocks/udprelay.go:232 +0xdb2
May 8 22:28:50 blake shadowsocks-go: created by github.com/shadowsocks/shadowsocks-go/shadowsocks.ReadAndHandleUDPReq
May 8 22:28:50 blake shadowsocks-go: /usr/local/go/src/github.com/shadowsocks/shadowsocks-go/shadowsocks/udprelay.go:256 +0xf1