v2.15.1-beta API issue
@xmrig 
I have around 39 Workers connecting to proxy, this issue happened after a miner connects a few minutes later I guess:
```
{
    "hashrate": {
        "total": [
            166.7,
            118.35,
            33.89,
            2.82,
            1.41,
            112.57
        ]
    },
    "mode": "rig_id",
    "workers": [
        [
            "test2",
            "2.3.4.5",
            1,
            3,
            0,
            0,
            3000675,
            1554132602249,
            0.0,
            0.0,
            0.83,
            0.06,
            0.03
        ],
        [
            "test",
            "1.2.3.4",
            0,
            0,
            0,
            0,
            0,
            0,
```


as you can see at the end of `/1/workers` , there is no `]` and it gave me this error:
`SyntaxError: JSON.parse: unexpected end of data at line 592 column 15 of the JSON data`

I'm using xmrig-proxy on ubuntu 16.04 server and I compiled it from source.

**UPDATE 1:**
OK this is wired because on my own laptop, I cant get `/1/workers` (I tried with both firefox and chrome), but on another VPS of mine, I can get the list even after connecting or disconnecting new miners.

**FIXED:**
It was an issue with ISP.