### Godot version

4.1.beta (7b1387ff2)

### System information

Mageia 9, Linux

### Issue description

When opening an empty project in latest `master`, I get these errors:
```
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: get_scene_path (editor/scu/../editor_data.cpp:880)
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: check_and_update_scene (editor/scu/../editor_data.cpp:683)
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: set_edited_scene (editor/scu/../editor_data.cpp:745)
```

Possibly related to recent changes to restore past sessions, but there's nothing to restore in this case?

### Steps to reproduce

- Create a new project, edit it
- Quit to project manager
- Re-open the newly created project -> errors

### Minimal reproduction project

Empty project.
_find_and_save_edited_subresources(scene, processed, flags);
	for (int i = 0; i < scene->get_child_count(); i++) {
		Node *n = scene->get_child(i);
		if (n->get_owner() != editor_data.get_edited_scene_root()) {
			continue;
		}
		_save_edited_subresources(n, processed, flags);
	}
}
void EditorNode::_find_node_types(Node *p_node, int &count_2d, int &count_3d) {
	if (p_node->is_class("Viewport") || (p_node != editor_data.get_edited_scene_root() && p_node->get_owner() != editor_data.get_edited_scene_root())) {
		return;
	}
	if (p_node->is_class("CanvasItem")) {
		count_2d++;
	} else if (p_node->is_class("Node3D")) {
		count_3d++;
	}
	for (int i = 0; i < p_node->get_child_count(); i++) {
		_find_node_types(p_node->get_child(i), count_2d, count_3d);
	}
}
void EditorNode::_save_scene_with_preview(String p_file, int p_idx) {