No response from MQTT Binding readProperty method

I apologize for the inconvenience, but I need your confirmation on the following issues.

# Problem

There is no response when I call readProperty on MQTT Binding.
A sample program is placed below.
https://github.com/hidetak/test-node-wot/tree/main/no-response-mqtt-read-property

Also, if observeProperty is executed and then writeProperty is executed, the written value can be retrieved, but sometimes it is retrieved twice.

# environment

* Mac(Apple siicon)
* OS: Sonoma 14.1
* nodejs: v18 or v20
* node-wot: 0.8.12

# Steps to reproduce

get the following code

https://github.com/hidetak/test-node-wot/tree/main/no-response-mqtt-read-property

1. $ npm install
1. $ npm run start:server
1. open new terminal
1. $ npm run start:client

When executed, the following string is output.
```
write property 100
observed count value is: 100
```
Expectations are as follows.
```
count value is: 0
write property 100
observed count value is: 100
```
Sometimes `observed count value is: 100` is output twice
```
write property 100
observed count value is: 100
observed count value is: 100
```

I apologize if there is a problem with my usage.