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.

Commencez par reproduire le flux de vote ZeroTalk décrit dans l’issue et inspectez le chemin de requête WebSocket dans UiWebsocket.py autour de la ligne 80 et des lignes 415-473, ainsi que dans MergerSitePlugin.py autour des lignes 206-212. Suivez pourquoi la publication de data/users/myaddress/data.json signale un fichier content.json invalide, puis vérifiez que le vote se termine ou présente une erreur exploitable.

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