### 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.
EditorProgress save("save", TTR("Saving Scene"), 4);
	if (editor_data.get_edited_scene_root() != nullptr) {
		save.step(TTR("Analyzing"), 0);
		int c2d = 0;
		int c3d = 0;
		_find_node_types(editor_data.get_edited_scene_root(), c2d, c3d);
		save.step(TTR("Creating Thumbnail"), 1);
		
		Ref<Image> img;
		
		
		
		if (c3d == 0 && c2d == 0) {
			img.instantiate();
			img->initialize_data(1, 1, false, Image::FORMAT_RGB8);
		} else if (c3d < c2d) {
			Ref<ViewportTexture> viewport_texture = scene_root->get_texture();
			if (viewport_texture->get_width() > 0 && viewport_texture->get_height() > 0) {
				img = viewport_texture->get_image();