1. Create a Terrain Object in your scene
2. Create a Prefab object where the parent object does not have a Mesh Renderer component on it
3. Attempt to paint this prefab onto the terrain under Paint Details

Actual Results: Nothing is visibly painted onto the Terrain Object, and there is no warning presented to the user that this scenario is not supported.
Expected Results: Either user's would be able to paint prefabs like this onto the Terrain object, or there would be a clear warning to the user that this is not supported.

Note: Terrain Tree painting has a warning for this situation to inform the user this is not supported, but Terrain Details does not