Fix: wechat protocol is not working if no obfs string is configured

transport/hysteria/obfs/dummy.go

@@ -0,0 +1,18 @@
+package obfs
+
+type DummyObfuscator struct{}
+
+func NewDummyObfuscator() *DummyObfuscator {
+	return &DummyObfuscator{}
+}
+
+func (x *DummyObfuscator) Deobfuscate(in []byte, out []byte) int {
+	if len(out) < len(in) {
+		return 0
+	}
+	return copy(out, in)
+}
+
+func (x *DummyObfuscator) Obfuscate(in []byte, out []byte) int {
+	return copy(out, in)
+}