### 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.
}
		}
		for (int i = 0; i < vsplits.size(); i++) {
			bool in_use = dock_slot[i * 2 + 0]->get_tab_count() || dock_slot[i * 2 + 1]->get_tab_count();
			if (in_use) {
				vsplits[i]->show();
			} else {
				vsplits[i]->hide();
			}
		}
		if (!p_keep_selected_tabs) {
			for (int i = 0; i < DOCK_SLOT_MAX; i++) {
				if (dock_slot[i]->is_visible() && dock_slot[i]->get_tab_count()) {
					dock_slot[i]->set_current_tab(0);
				}
			}
		}
		if (right_l_vsplit->is_visible() || right_r_vsplit->is_visible()) {
			right_hsplit->show();
		} else {
			right_hsplit->hide();
		}
	}
}
void EditorNode::_dock_tab_changed(int p_tab) {
	
	if (!docks_visible) {
		for (int i = 0; i < DOCK_SLOT_MAX; i++) {
			dock_slot[i]->hide();
		}