Duplicate entry in offline file

[nilsbehlen]

If the offline values are emtpy and the offline refill fails (because the system is offline), the next offline refill try while being online creates another json object in the offline file resulting in the following:
"offline": [
{
"count": "20",
"refilltoken": "old refill token",
"response": null,
"serial": "serial",
"user": "",
"username": "username"
},
{
"count": "20",
"refilltoken": "new refill token",
"response": { ...,
....
},
"serial": "serial",
"user": "",
"username": "username"
}
]