[Bug] Base64 `img` data deleted within `html` for `Choices` or `List`

**Describe the bug**

While LabelStudio's `Image` tags display base64 correctly, I can't put base64 strings within an `img` tag for the `html` fields for `Choices` or `List`. The `src` field gets completely deleted in the displayed UI (see screenshot), even though I can clearly see that the fields are in the uploaded data (see screenshot). I've also confirmed that using a hosted URL works for `src` so it seems like a base64 issue.

**To Reproduce**
Steps to reproduce the behavior:
1. Create a template with `Choices`
2. Supply values with `html` that contains `img` tags with base64 source

```

```

```
{
"values": [
{
"id": "1",
"title": "title",
"value": "value",
"html": ""
}
]
}
```

**Expected behavior**
The `img` tag should display the base64 value.

**Screenshots**


**Environment (please complete the following information):**
- OS: [e.g. iOS]: Deployed
- Label Studio Version [e.g. 0.8.0]: 1.15.0

**Additional context**
Add any other context about the problem here.