Unable to decode multipart header with fluxzy Desktop

Typically this kind of payload reproductible with .NET HTTPClient just fail to be decoded.

```csharp
        using var content = new MultipartFormDataContent
        {
            { new ByteArrayContent(_buffer, 0, length), "file", "image.png" }
        };

        var response = await HttpClient.PostAsync("some/url", content);
```