External sites do not have an icon in the menu in the sandwich menu of Android app

### ⚠️ Before posting ⚠️

- [X] This is a **bug**, not a question or an enhancement.
- [X] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [X] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [X] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

1. Install External sites app
2. Create an external site inside of it
3. Add custom icon
4. Observe the icon and the element is shown in webUI
5. Observe that the icon is not rendered in the android client app, while the text of menu item is present.

### Expected behaviour

The custom icon is show in the menu of android app.

### Actual behaviour

The icon is not show in the menu of android app.

### Android version

13.0

### Device brand and model

Pixel 5A

### Stock or custom OS?

Stock

### Nextcloud android app version

3.25.0

### Nextcloud server version

26.0.4

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

_No response_

### Additional information

_No response_