Fix `unacceptable kind of object to dump` error

When an example's `reportedProperties` attribute is NOT populated, you get an error that looks like this:

[An example Failure](https://github.com/Azure/azure-rest-api-specs-pr/runs/15552555014)


[Last commit that eliminated this error](https://github.com/Azure/azure-rest-api-specs-pr/pull/13740/commits/5d06a6bec03f582415896db9f9d7cfa5ea3209f8)

Effectively, I believe the issue is when we have objects with 0 value within the `reportedProperties` object on an example where they are being expected to be present, the error that is generated is just...wrong.

There's a PROBLEM here, we're expecting these examples to have some value here, but `oav` should just be reporting the missing expectations, rather than _failing to dump_ the json.