fix for argp usage

src/ebusd/datahandler.cpp

@@ -31,7 +31,7 @@ using namespace std;
 static const struct argp_child g_last_argp_child = {NULL, 0, NULL, 0};
 
 /** the list of @a argp_child structures. */
-static const struct argp_child* g_argp_children[
+static struct argp_child g_argp_children[
 #ifdef HAVE_MQTT
 						1
 #endif
@@ -42,11 +42,11 @@ const struct argp_child* datahandler_getargs()
 {
 	size_t count = 0;
 #ifdef HAVE_MQTT
-	g_argp_children[count++] = mqtthandler_getargs();
+	g_argp_children[count++] = *mqtthandler_getargs();
 #endif
 	if (count>0) {
-		g_argp_children[count] = &g_last_argp_child;
+		g_argp_children[count] = g_last_argp_child;
-		return g_argp_children[0];
+		return g_argp_children;
 	}
 	return NULL;
 }

src/ebusd/mqtthandler.cpp

@@ -69,7 +69,7 @@ static error_t mqtt_parse_opt(int key, char *arg, struct argp_state *state)
 	return 0;
 }
 
-static struct argp g_mqtt_argp = { g_mqtt_argp_options, mqtt_parse_opt, NULL, NULL, NULL, NULL, NULL };
+static const struct argp g_mqtt_argp = { g_mqtt_argp_options, mqtt_parse_opt, NULL, NULL, NULL, NULL, NULL };
 static const struct argp_child g_mqtt_argp_child = {&g_mqtt_argp, 0, "", 1};
 
 const struct argp_child* mqtthandler_getargs()
@@ -151,6 +151,9 @@ MqttHandler::MqttHandler(BusHandler* busHandler, MessageMap* messages)
 		logOtherError("mqtt", "malformed topic %s", g_topic);
 		return;
 	}
+	if (!enabled) {
+		return;
+	}
 	if (m_topicCols.empty()) {
 		if (m_topicStrs.empty()) {
 			m_topicStrs.push_back("");