Filters do not work in GetFundamentalDataAsync

Send the following request:

```csharp
api.GetFundamentalDataAsync("AAPL.US", "Financials")
```
All properties in the returned `FundamentalData` object are `null`.

Send the request without filtering:

```csharp
api.GetFundamentalDataAsync("AAPL.US")
```

All properties in the returned `FundamentalData` object, including `Financials`, are populated.

package version: 1.3.4.5