Fix memory leak for broker to remote broker connection

src/TinyMqtt.cpp

@@ -37,6 +37,7 @@ MqttBroker::~MqttBroker()
 #ifdef EPOXY_DUINO
   instances--;
 #endif
+  closeRemoteBroker();
   while(clients.size())
   {
     auto client = clients[0];
@@ -155,9 +156,19 @@ void MqttBroker::addClient(MqttClient* client)
   clients.push_back(client);
 }
 
+void MqttBroker::closeRemoteBroker()
+{
+  if (remote_broker)
+  {
+    delete remote_broker;
+    remote_broker = nullptr;
+  }
+}
+
 void MqttBroker::connect(const string& host, uint16_t port)
 {
   debug("MqttBroker::connect");
+  closeRemoteBroker();
   if (remote_broker == nullptr) remote_broker = new MqttClient;
   remote_broker->connect(host, port);
   remote_broker->local_broker = this;  // Because connect removed the link

src/TinyMqtt.h

@@ -209,8 +209,8 @@ class MqttClient
     ~MqttClient();
 
     void connect(MqttBroker* local_broker);
-    void connect(string broker, uint16_t port, uint16_t keep_alive = 10);
-    void connect(const IPAddress& ip, uint16_t port, uint16_t keep_alive = 10)
+    void connect(string broker, uint16_t port = 1883, uint16_t keep_alive = 10);
+    void connect(const IPAddress& ip, uint16_t port = 1883, uint16_t keep_alive = 10)
     { connect(ip.toString().c_str(), port, keep_alive); }
 
     // TODO it seems that connected returns true in tcp mode even if
@@ -387,6 +387,8 @@ class MqttBroker
     const char* auth_password = "guest";
     MqttClient* remote_broker = nullptr;
 
+    void closeRemoteBroker();
+
     void retain(const Topic& topic, const MqttMessage& msg);
     void retainDrop();