fix: populate defaults for nested dependencies when formData is undefined

[epicfaace]

Reasons for making this change

Fixes #1311. It looks like the problem is that formData is not defaulted to {} when populating defaults for dependencies, so then when formData is undefined / null, it crashes.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
  • I've run npm run cs-format on my branch to conform my code to prettier coding style
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[jrose-carecloud]

If formData is null this wont work as it wont default to the empty object

[epicfaace]

@jrose-carecloud I added a test with null and it seems to work; was there something specifically that didn't work when you tried it?

[jrose-carecloud]

I'l admit that I didnt run the test, more of a just glancing sort of thing. But argument defaults only occur when the argument is undefined, not null.
Consider:

function foo(bar = {}) {
   console.log(bar);
}

If called like this:

foo();

We will log out {} as expected. But if called like this:

foo(null)

We will log out, null.

If null is not a possible/acceptable value to be received here then please disregard. I'm just keeping a close eye on this issue as its effecting our app at the moment.

IMO a safer approach would be:

function computeDefaults(schema, parentDefaults, definitions, rawFormData) {
  const formData = isObject(rawFormData) ? rawFormData : {}

[epicfaace]

That's a good point, thanks. I don't think my null test accounted for that case, because it was still probably passing undefined down to the actual computeDefaults function. I'll fix this PR accordingly.

[glasserc]

This feels kind of like a bandaid, but let's merge it so we can get a patch out.