Error when data value is undefined

### Our code:
```
betterAjvErrors(
lightdashDbtYamlSchema,
schemaFile,
validate.errors || [],
{ indent: 2 },
);
```

### Values:

**schemaFile** is `undefined`

**validate.errors** is
```
[
{
instancePath: '',
schemaPath: '#/type',
keyword: 'type',
params: { type: 'object' },
message: 'must be object'
}
]
```

### Error:
```
e TypeError: Cannot read properties of undefined (reading 'charAt')
at next (/Users/joserego/Documents/lightdash/node_modules/@humanwhocodes/momoa/api.js:235:22)
at tokenize (/Users/joserego/Documents/lightdash/node_modules/@humanwhocodes/momoa/api.js:491:13)
at parse (/Users/joserego/Documents/lightdash/node_modules/@humanwhocodes/momoa/api.js:726:20)
at Object.src_default (/Users/joserego/Documents/lightdash/packages/cli/node_modules/better-ajv-errors/lib/cjs/index.js:31:42)
at /Users/joserego/Documents/lightdash/packages/cli/dist/dbt/schema.js:55:49
at Generator.next ()
at fulfilled (/Users/joserego/Documents/lightdash/packages/cli/dist/dbt/schema.js:24:58)
```

### Workaround

By making sure the data defaults to an empty string or an empty object or null.
```
betterAjvErrors(
lightdashDbtYamlSchema,
schemaFile || '',
validate.errors || [],
{ indent: 2 },
);
```
And with this get the proper error:
```
TYPE must be object

> 1 | ""
| ^^ 👈🏽 type must be object
```

### Solution:

`better-ajv-errors` could make sure `data` can't be undefined.
Or support undefined and have an appropriate message.

Start at the better-ajv-errors API that receives the undefined data value and reproduce the call shown in the issue. Trace how that value reaches parsing, then determine whether completion should reject undefined clearly or support it with an appropriate validation message; the existing empty-string workaround provides the expected failure context.

Written by the indexing model from the issue text.