### 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.
Node *scene = editor_data.get_edited_scene_root();
	if (!scene) {
		return;
	}
	List<String> esl;
	p_config_file->get_section_keys("editor_states", &esl);
	Dictionary md;
	for (const String &E : esl) {
		Variant st = p_config_file->get_value("editor_states", E);
		if (st.get_type() != Variant::NIL) {
			md[E] = st;
		}
	}
	editor_data.set_editor_plugin_states(md);
}
void EditorNode::_save_editor_states(const String &p_file, int p_idx) {