AgilesGetAsync does not correctly populate issue custom fields

I have the following code to pull agile boards, sprints and issues

```
var client = await connection.GetAuthenticatedApiClient();
var result = await client.AgilesGetAsync(fields: "name,id,owner(id,name,fullname),sprints(id,agile(name),name,start,unresolvedIssuesCount,issues(idReadable,summary,customFields(name,value)),start)");
```

## Expected behaviour

The name and value of the custom fields should be populated

## Actual behaviour

The name is populated but the value isn't.

However, if I change the fields from this

`customFields(name,value)`

to this

`customFields(name,value(id,fullName))`

The output changes from this


to this


What seems to be happening is anything with an ID or a FullName child property is populated.

However the simple properties always seem to be null.