fixup! proto/msgpack: Fix encoding INVALID_{TID,OID}

go/neo/proto/protogen.go

@@ -1012,7 +1012,7 @@ func (e *encoderM) genBasic(path string, typ *types.Basic, userType types.Type)
 	// zodb.Tid and zodb.Oid are encoded as [8]bin or nil
 	if userType == zodbTid || userType == zodbOid {
 		e.emit("if %s == %v {", path, INVALID_ID)   // INVALID_{TID,OID} =>
-		e.emit("data[%v] = msgpack.Nil", e.n)     // mnil
+		e.emit("data[%v] = byte(msgpack.Nil)", e.n) // mnil
 		e.emit("data = data[%v:]", e.n + 1)
 		e.emit("} else {")
 		e.emit("data[%v] = byte(msgpack.Bin8)", e.n);  e.n++