BUG: json_normalize generates ```TypeError: 'NoneType' object is not subscriptable``` as `metadata` object is not always present.
The example below always generate an error ```TypeError: 'NoneType' object is not subscriptable``` as `metadata` object is not always present.
```
file = [{'values': ['1', '2'], 'metadata': {'name': 'first_value'}},
        {'values': ['3', '4'], 'metadata': None}]

df = json_normalize(file,
                    record_path='values',
                    meta=[['metadata', 'name']],
                    errors='ignore')
```
The `metadata` object is dynamic and nested, so I am concerned why it doesn't generate something like this:

| 0 | metadata.name |
|---|---------------|
| 1 | first_value   |
| 2 | first_value   |
| 3 | nan           |
| 4 | nan           |

as I set ```errors='ignore' ```

@WillAyd Could you please explain the best way to handle this?

_Originally posted by @sann05 in https://github.com/pandas-dev/pandas/issues/21830#issuecomment-725439522_