msgRef.current is null but got check undefined in the ContentEditable component causing app crashed

I am facing an error that it'll crash the app entirely. When I traced the error, it shows into this part:
```
if (typeof msgRef.current === "undefined") {
return true;
}
```



Based on the error, I think the above line should be checking for null not undefined right. Someone please help, thanks a lot!!

_Originally posted by @tunglamforwork in https://github.com/chatscope/chat-ui-kit-react/discussions/173_

Start in the ContentEditable component and inspect the msgRef.current check shown in the issue. Reproduce the reported crash or trace the null-ref path, then verify that the component no longer crashes when the ref is null and that existing behavior remains unchanged.

Written by the indexing model from the issue text.