### 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.
current_menu_option = -1;
	if (accept) {
		accept->set_ok_button_text(p_title);
		accept->set_text(p_text);
		EditorInterface::get_singleton()->popup_dialog_centered(accept);
	}
}
void EditorNode::show_save_accept(const String &p_text, const String &p_title) {
	current_menu_option = -1;
	if (save_accept) {
		save_accept->set_ok_button_text(p_title);
		save_accept->set_text(p_text);
		EditorInterface::get_singleton()->popup_dialog_centered(save_accept);
	}
}
void EditorNode::show_warning(const String &p_text, const String &p_title) {
	if (warning) {
		warning->set_text(p_text);
		warning->set_title(p_title);
		EditorInterface::get_singleton()->popup_dialog_centered(warning);
	} else {
		WARN_PRINT(p_title + " " + p_text);
	}
}
void EditorNode::_copy_warning(const String &p_str) {