cleanup presence data

Network.cpp

@@ -148,7 +148,7 @@ void Network::update()
         }
     }
 
-    if(_presenceCsv != nullptr)
+    if(_presenceCsv != nullptr && strlen(_presenceCsv) > 0)
     {
         publishString(mqtt_topic_presence, _presenceCsv);
         _presenceCsv = nullptr;

PresenceDetection.cpp

@@ -46,6 +46,8 @@ void PresenceDetection::update()
         }
     }
 
+    _csv[_csvIndex-1] = 0x00;
+
     _network->publishPresenceDetection(_csv);
 }