For input string: "00000null" error during BLE.write call

Ionic Framework ionic-v3
1

Messages I get back include:
BLE WRITE THEN
For input string: “00000null”

    this.ble.connect(id).subscribe(datos=>{
      this.setMessage("BLE CONNECT SUBSCRIBE: BEGIN. Doing ble write...");
      this['valor'] = 1;
      this.ble.write(this['targetDevice'].id, this['targetDevice'].service_id,this['targetDevice'].service_id, this['valor'].buffer ).then(()=>{
        this.setMessage("BLE WRITE THEN!");
        this.ble.disconnect(id);
      },(error)=>{
        this.setMessage("BLE Write ERROR!");
        this.setMessage(error);
      });
    },error=>{
      this.setMessage("BLE Connect ERROR!");
      this.setMessage(error.message);
    });