[fpc-pascal] Null values with JSON RPC

[Ryan Joseph]

I'm trying to get the pascal language server working on Visual Studio Code and during testing I found that sending null values to the server is causing problems. i.e.:

...
    "processId": 3997,
    "clientInfo": {
        "name": "vscode",
        "version": "1.47.3"
    },
    "rootPath": null,
    "rootUri": null,
...

This is translated by the RPC layer to a message like:

{"jsonrpc":"2.0","error":{"code":-32603,"message":"Cannot convert data from Null value"},"id":1}

According to the protocol null values are allowed so is there a  way I can accept null values gracefully instead of failing with an error? In particular rootPath is trying to be mapped to a string so it could be translated to just '' and that would be better than giving this error that prevents the server from working entirely and causes very confusing errors that are hard to debug.

Regards,
	Ryan Joseph