Meross Power Strip (MSS420F) Not Working
This is the output I get from the Homebridge console logs

```json
(node:838) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'digest' of undefined
    at Meross.getOnCharacteristicHandler (/usr/lib/node_modules/homebridge-meross/index.js:327:34)
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
(node:838) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 4)
```

My config is:

```json
        {
            "model": "MSS420F",
            "name": "Meross Strip",
            "deviceUrl": "192.168.1.199",
            "channel": 0,
            "messageId": "69f51bd4a3cee4bb3a0c9df9b5",
            "timestamp": 1592957079,
            "sign": "ef7dbc1e630b7242376bbacea5e3c89",
            "accessory": "Meross"
        }
```

I'm using HTTP Catcher, it returns a valid 200 response.

I originally posted on Reddit regarding the power strip, sorry it took so long!