verify sign error: ValueError: Extra data: line 3140 column 2 - line 3140 column 103

### Step 1: Please describe your environment

* ZeroNet version: 0.6.1 r2324
* Operating system: Debian buster
* Web browser: 52.6.0
* Tor status: always
* Opened port: yes
* Special configuration: in /etc/tor
```
ControlPort 9051
CookieAuthentication 1
```

From https://zeronet.readthedocs.io/en/latest/faq/#how-to-make-zeronet-work-with-tor-under-linux

### Step 2: Describe the problem:

Got the following output while running zeronet

[11:52:49] Site:1PLAYg..Xvfp content.json: verify sign error: ValueError: Extra data: line 3140 column 2 - line 3140 column 103 (char 108699 - 108800) in ContentManager.py line 821 > __init__.py line 291 > __init__.py line 339 > decoder.py line 367

#### Steps to reproduce:

#### Observed Results:

The same as above.

#### Expected Results:

The error should not be there.

If such an error does happen, at least give some hint as to where I should look next to resolve it.