Error on the 'Files' tab

### Step 1: Please describe your environment

* ZeroNet version: 0.6.1 r3229, Python 2.7.14 (default, Jan 5 2018, 10:41:29)
[GCC 7.2.1 20171224], Gevent: 1.2.2
* Operating system: ArchLinux
* Web browser: Chromium 64.0.3282.140 (Developer Build) (64-bit)
* Tor status: always
* Opened port: no
* Special configuration: -

### Step 2: Describe the problem:
Got the following error every time opening 'Files' tab on ZeroHello:
```
[12:11:16] Site:1HeLLo..Tf3D WebSocket handleRequest error: AttributeError: 'bool' object has no attribute 'get' in UiWebsocket.py line 81 > UiWebsocket.py line 254 > UiWebsocketPlugin.py line 134 > UiWebsocketPlugin.py line 47
{"cmd":"optionalFileList","params":{"address":"all","filter":"downloaded,bigfile","limit":101,"orderby":"time_downloaded DESC"},"wrapper_nonce":"6ed98bb38f0a33bbe7200f7d4487073d0b720e060515167206294d964ce40e0c","id":36}
```

#### Steps to reproduce:

1. Open the 'Files' tab on ZeroHello.

#### Observed Results:


#### Expected Results:

Errorlessness.

Start by reproducing the error from the ZeroHello Files tab and trace the optionalFileList request through UiWebsocket.py and UiWebsocketPlugin.py, using the reported stack locations. Done means the Files tab opens without the reported AttributeError for the given request.

Rédigé par le modèle d'indexation à partir du texte de l'issue.