Mqtt: fix panic publishing nil interface

server/mqtt.go

@@ -14,6 +14,7 @@ import (
 	"github.com/evcc-io/evcc/core/vehicle"
 	"github.com/evcc-io/evcc/plugin/mqtt"
 	"github.com/evcc-io/evcc/util"
+	"github.com/samber/lo"
 )
 
 // MQTT is the MQTT server. It uses the MQTT client for publishing.
@@ -53,7 +54,7 @@ func NewMQTT(root string, site site.API) (*MQTT, error) {
 
 func (m *MQTT) encode(v any) string {
 	// nil should erase the value
-	if v == nil {
+	if v == nil || lo.IsNil(v) {
 		return ""
 	}
 

server/mqtt_test.go

@@ -97,6 +97,13 @@ func (suite *mqttSuite) TestSlice() {
 	suite.Equal([]string{"2", "10", "20"}, suite.payloads, "payloads")
 }
 
+func (suite *mqttSuite) TestNilInterface() {
+	var ptr *time.Time
+	suite.publish("test", false, ptr)
+	suite.Equal([]string{"test"}, suite.topics, "topics")
+	suite.Equal([]string{""}, suite.payloads, "payloads")
+}
+
 func (suite *mqttSuite) TestMeasurement() {
 	topics := lo.Map([]string{
 		"title", "icon", "power", "energy", "powers", "currents", "excessDCPower", "capacity", "soc", "controllable", "forecast",