The content submission is in progress but nothing happen - Exception: Invalid content.json file

### Step 1: Please describe your environment

* ZeroNet version: 0.7.2 r4548, Python 3.7.3
* Operating system: Linux Arch
* Web browser: FF
* Tor status: available
* Opened port: yes
* Special configuration: multiuser

### Step 2: Describe the problem:

#### Steps to reproduce:

i have tried to like someone's topic from within index page of the ZeroTalk. It was only animating the vote button and nothing else.
The debug.log though shows something relevant:
> Site:1TaLkF..jipT WebSocket handleRequest error: Exception: Invalid content.json file: data/users/myaddress/data.json in UiWebsocket.py line 80 > 236 > MergerSite/MergerSitePlugin.py line 212 > 206 > UiWebsocket.py line 473 > MergerSite/MergerSitePlugin.py line 209 > 206 > OptionalManager/UiWebsocketPlugin.py line 41 > UiWebsocket.py line 415
> {"cmd":"sitePublish","params":{"inner_path":"data/users/myaddress/data.json"},"wrapper_nonce":"somestringhere","id":11}
>

So maybe ZeroNet can either fix the file on background or print some error on page so one knows how to fix this issue...

I have checked that data.json using online validator and it says it is valid and content.json seems OK too.