Failed to save cached accessories to disk

### What issue do you have? Please be as thorough and explicit as possible.
Failed to save cached accessories to disk

### Details of your setup.
* Do you use (1) Homebridge UI-X (2) Homebridge CLI or (3) HOOBS? 
(1) Homebridge

* Which version of Homebridge/HOOBS do you have?
v1.3.4

* Which platform do you run Homebridge/HOOBS on (e.g. Raspberry Pi/Windows/HOOBS Box)? Please also mention your version of Node.js/NPM if known.
Mac OS X, 
Node.js Version | v14.17.5
Npm Version | v7.20.5

* Which version of this plugin (homebridge-meross) do you have? Has the issue started since upgrading from a previous version?
homebridge-meross v6.7.0, I started having issues after upgrading

* Which Meross devices do you have that are causing issues? Please include product models if applicable.
MSL-120D, but it is detecting all my meross devices (HomeKit native), these include: MSS510X, MSS550X

### Please paste any relevant logs below.

```
[8/16/2021, 11:57:08 AM] Failed to save cached accessories to disk: Converting circular structure to JSON
    --> starting at object with constructor 'TLSSocket'
    |     property 'parser' -> object with constructor 'HTTPParser'
    --- property 'socket' closes the circle
[8/16/2021, 11:57:08 AM] Your accessories will not persist between restarts until this issue is resolved.
[8/16/2021, 11:57:08 AM] [Meross] [Computer Side Lamp] has been reported [online].
[8/16/2021, 11:57:08 AM] Failed to save cached accessories to disk: Converting circular structure to JSON
    --> starting at object with constructor 'TLSSocket'
    |     property 'parser' -> object with constructor 'HTTPParser'
    --- property 'socket' closes the circle
[8/16/2021, 11:57:08 AM] Your accessories will not persist between restarts until this issue is resolved.
[8/16/2021, 11:57:08 AM] [Meross] [Fan Light] has been reported [online].
[8/16/2021, 11:57:08 AM] [homebridge-weather-plus] This plugin generated a warning from the characteristic 'Air Pressure': Characteristic not in required or optional characteristic section for service TemperatureSensor. Adding anyway.. See https://git.io/JtMGR for more info.
[8/16/2021, 11:57:08 AM] [homebridge-weather-plus] This plugin generated a warning from the characteristic 'Current Relative Humidity': Characteristic not in required or optional characteristic section for service TemperatureSensor. Adding anyway.. See https://git.io/JtMGR for more info.
[8/16/2021, 11:57:08 AM] Failed to save cached accessories to disk: Converting circular structure to JSON
    --> starting at object with constructor 'TLSSocket'
    |     property 'parser' -> object with constructor 'HTTPParser'
    --- property 'socket' closes the circle
[8/16/2021, 11:57:08 AM] Your accessories will not persist between restarts until this issue is resolved.
[8/16/2021, 11:57:08 AM] [Meross] [Desk Lamp] has been reported [online].
[8/16/2021, 11:57:08 AM] Failed to save cached accessories to disk: Converting circular structure to JSON
    --> starting at object with constructor 'TLSSocket'
    |     property 'parser' -> object with constructor 'HTTPParser'
    --- property 'socket' closes the circle
[8/16/2021, 11:57:08 AM] Your accessories will not persist between restarts until this issue is resolved.
[8/16/2021, 11:57:08 AM] [Meross] [Jorge’s baseball lamp] has been reported [online].
```
