Discard empty MQTT topics when subscribing

code/espurna/mqtt.ino

@@ -65,7 +65,7 @@ void mqttSend(const char * topic, const char * message) {
 }
 
 void mqttSubscribeRaw(const char * topic) {
-    if (mqtt.connected()) {
+    if (mqtt.connected() && (strlen(topic) > 0)) {
         DEBUG_MSG("[MQTT] Subscribing to %s\n", topic);
         mqtt.subscribe(topic, MQTT_QOS);
     }
@@ -144,7 +144,6 @@ void _mqttOnMessage(char* topic, char* payload, unsigned int len) {
     }
 
     // Send message event to subscribers
-    // Topic is set to the specific part each one might be checking
     for (unsigned char i = 0; i < _mqtt_callbacks.size(); i++) {
         (*_mqtt_callbacks[i])(MQTT_MESSAGE_EVENT, topic, message);
     }

code/html/index.html

@@ -417,12 +417,12 @@
 
                                 <div class="pure-g">
                                     <label class="pure-u-1 pure-u-md-1-4" for="mqttServer">MQTT Server</label>
-                                    <input class="pure-u-1 pure-u-md-3-4" name="mqttServer" type="text" size="20" tabindex="21" placeholder="MQTT Server" />
+                                    <input class="pure-u-1 pure-u-md-3-4" name="mqttServer" type="text" size="20" tabindex="21" placeholder="IP or address of your broker" />
                                 </div>
 
                                 <div class="pure-g">
                                     <label class="pure-u-1 pure-u-md-1-4" for="mqttPort">MQTT Port</label>
-                                    <input class="pure-u-1 pure-u-md-3-4" name="mqttPort" type="text" size="6" tabindex="22" placeholder="1883" />
+                                    <input class="pure-u-1 pure-u-md-3-4" name="mqttPort" type="text" size="6" tabindex="22" value="1883" />
                                 </div>
 
                                 <div class="pure-g">
@@ -470,12 +470,12 @@
 
                                 <div class="pure-g">
                                     <label class="pure-u-1 pure-u-md-1-4" for="dczTopicIn">Domoticz IN Topic</label>
-                                    <input class="pure-u-1 pure-u-md-3-4" name="dczTopicIn" type="text" tabindex="31" placeholder="domoticz/in" />
+                                    <input class="pure-u-1 pure-u-md-3-4" name="dczTopicIn" type="text" tabindex="31" />
                                 </div>
 
                                 <div class="pure-g">
                                     <label class="pure-u-1 pure-u-md-1-4" for="dczTopicOut">Domoticz OUT Topic</label>
-                                    <input class="pure-u-1 pure-u-md-3-4" name="dczTopicOut" type="text" tabindex="32" placeholder="domoticz/out" />
+                                    <input class="pure-u-1 pure-u-md-3-4" name="dczTopicOut" type="text" tabindex="32" />
                                 </div>
 
                                 <div class="pure-g module module-dht module-ds">