### 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.
if (p_editing_owner) {
		const ObjectID id = p_editing_owner->get_instance_id();
		for (EditorPlugin *plugin : active_plugins[id]) {
			_plugin_over_edit(plugin, nullptr);
		}
		active_plugins.erase(id);
	} else {
		
		
		List<ObjectID> to_remove;
		for (KeyValue<ObjectID, HashSet<EditorPlugin *>> &kv : active_plugins) {
			if (!ObjectDB::get_instance(kv.key)) {
				to_remove.push_back(kv.key);
				for (EditorPlugin *plugin : kv.value) {
					_plugin_over_edit(plugin, nullptr);
				}
			}
		}
		for (const ObjectID &id : to_remove) {
			active_plugins.erase(id);
		}
	}
}
static bool overrides_external_editor(Object *p_object) {