Test unmarshal nil for port

config/type_port.go

 		return nil
 	}
 
-	intValue, err := strconv.ParseUint(string(data), 10, 16)
+	intValue, err := strconv.ParseUint(string(data), 10, 64)
 	if err != nil {
 		return fmt.Errorf("port number is not a number: %w", err)
 	}

config/type_port_test.go

 	suite.Suite
 }
 
+func (suite *TypePortTestSuite) TestUnmarshalNil() {
+	typ := &config.TypePort{}
+	suite.NoError(typ.UnmarshalJSON(nil))
+	suite.Equal("0", typ.String())
+}
+
 func (suite *TypePortTestSuite) TestUnmarshalFail() {
 	testData := []int{
 		-1,