no preview of time series when header attributes are quoted

**Describe the bug**
Cannot view the time series data in labeling task preview when the dataset header attributes are quoted.

**To Reproduce**
Steps to reproduce the behavior:
Create a local data source and add location for dataset (below first few rows)
```
"timestamps","value","anomaly","changepoint","trend","noise","seasonality1","seasonality2","seasonality3"
1416722400,-363.27890932679,0,0,-2,-361.27890932679,0,0,0
1416726000,320.888589880355,0,0,-4,-217.845823831664,413.1,115.769758874358,13.8646548376615
1416729600,891.727421717808,0,0,-6,-69.1426855907418,715.510188606703,223.65,27.7099187018461
1416733200,1174.65228740956,0,0,-8,-1.35300355429298,826.2,316.288863224743,41.5164277391066
1416736800,1712.29026109409,0,0,-10,564.14203707648,715.510188606703,387.373163112779,55.2648722981255
1416740400,1081.23695929409,0,0,-12,179.14231325898,413.1,432.0586220991,68.9360239360087
1416744000,328.359752757442,0,0,-14,-187.451009553559,1.01180318545554e-13,447.3,82.5107623110014
```
Create project with following task (adjust path and filename accordingly)
```
[{
"data": {
"csv": "http://localhost:8080/data/local-files?d=online-SESD/A3Benchmark-TS1.csv"
}
}]
```
Labeling UI was configured as follows
```

```
Go to project and select labeling task. See that preview panel remains gray.
When I remove the double quotes from the time series dataset, I see the time series data in the task.

```
timestamps,value,anomaly,changepoint,trend,noise,seasonality1,seasonality2,seasonality3
1416722400,-363.27890932679,0,0,-2,-361.27890932679,0,0,0
1416726000,320.888589880355,0,0,-4,-217.845823831664,413.1,115.769758874358,13.8646548376615
1416729600,891.727421717808,0,0,-6,-69.1426855907418,715.510188606703,223.65,27.7099187018461
1416733200,1174.65228740956,0,0,-8,-1.35300355429298,826.2,316.288863224743,41.5164277391066
1416736800,1712.29026109409,0,0,-10,564.14203707648,715.510188606703,387.373163112779,55.2648722981255
1416740400,1081.23695929409,0,0,-12,179.14231325898,413.1,432.0586220991,68.9360239360087
1416744000,328.359752757442,0,0,-14,-187.451009553559,1.01180318545554e-13,447.3,82.5107623110014
```

**Expected behavior**
I would expect the data can be read with and without quoted header attributes.

**Environment (please complete the following information):**
I used the docker image of Label Studio 1.7