Initialize otaClient to nullptr as default

Author: pennam

src/ArduinoIoTCloudTCP.h

@@ -75,7 +75,7 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
     virtual void printDebugInfo() override;
 
     int begin(ConnectionHandler & connection, bool const enable_watchdog = true, String brokerAddress = DEFAULT_BROKER_ADDRESS_SECURE_AUTH, uint16_t brokerPort = DEFAULT_BROKER_PORT_SECURE_AUTH);
-    int begin(Client * mqttClient, Client * otaClient, bool const enable_watchdog = true, String brokerAddress = DEFAULT_BROKER_ADDRESS_SECURE_AUTH, uint16_t brokerPort = DEFAULT_BROKER_PORT_SECURE_AUTH);
+    int begin(Client * mqttClient, Client * otaClient = nullptr, bool const enable_watchdog = true, String brokerAddress = DEFAULT_BROKER_ADDRESS_SECURE_AUTH, uint16_t brokerPort = DEFAULT_BROKER_PORT_SECURE_AUTH);
 
     #ifdef BOARD_HAS_SECRET_KEY
     inline void setBoardId        (String const device_id) { setDeviceId(device_id); }