Error with SVG and file field with mime-type accept svg+xml

I have configured a plugin with a file upload field as follows:

```
type: file
...
multiple: true
limit: 0
filesize: 1
accept:
- image/svg+xml
```

When uploading an SVG to that file field, I receive the following error:
```
The MIME type "image/svg+xml" for the file "abacus.svg" is not an accepted.
```

The SVG mime-type appears to be accurately defined in the media section of my site configuration (all are left as default):

However, when I set the `accept` to `image/*`, the image upload works perfectly fine with the same SVG files. (The SVGs in question are Font Awesome Pro icons, in case that makes any difference).

**Version:**
- Grav: 1.6.11
- Grav Admin: 1.9.7