Function getNestedField in FormFIeld doesn't return correct value for objects containing arrays

[dvcanton]

Describe the bug
When using the FormField component in a form containing nested arrays (for example, the new sources field in Argo's application spec definition), the implemented function will not return the correct value for the field.

How to reproduce
Use an object containing an array as src parameter and a path inside the array.
Example:

src:
{
    "apiVersion": "argoproj.io/v1alpha1",
    "kind": "Application",
    "metadata": {
        "name": ""
    },
    "spec": {
        "destination": {
            "name": "",
            "namespace": "",
            "server": ""
        },
        "sources": [
            {
                "repoURL": "https://github.com/argoproj/argocd-example-apps.git",
                "name": "guestbook",
                "path": "guestbook",
                "ref": "guestbook"
            }
        ],
        "project": ""
    }
}

path: spec.sources[0].repoURL