Rendering error for XML image with text comment

**Steps to reproduce:**

Render any compound in image/svg+xml format with _two or more_ words as a comment.
```
from indigo import Indigo
from indigo.renderer import IndigoRenderer

i = Indigo()
ir = IndigoRenderer(i)

mol = i.loadMolecule("C")
i.setOption("render-output-format", "svg")
i.setOption("render-comment", "Any comment")
r = ir.renderToString(mol)
```
Or with this request body for /indigo/render ->
```
{
"data": {
"type": "render",
"attributes": {
"compound": {
"structure": "c",
"format": "auto"
},
"outputFormat": "image/svg+xml",
"options": {"render-comment": "Any comment"}
}
}
}
```

**Actual result:**
An image tag appears in XML, which makes it invalid and not suitable for rendering a correct image.

Additional lines in XML:
``

**Expected result:**
Valid XML-string, rendering correct image. E.g. something like this ->