Steps to reproduce:

1. Go to Admin -> Dashboards -> Predefined Dashboards -> Default dashboard.
2. Click on the "Preview" tab.

Result:
One is presented with an exception:

Expected result:
The preview should be loaded properly.

The preview applies to SiteContext paths (so, non-excluded ones via ibexa.system.<scope>.site_context.excluded_paths semantic config). Therefore the preview button should for these paths disappear the same way the SiteContext selectof form does. See the comment for more details.

Spec:

That preview for Dashboard content type needs to be loaded for admin SiteAccess with dashboard view type, the same way we implemented it for Dashboard Builder  preview.