### 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.
dock_slot[i]->show();
			}
			WindowWrapper *wrapper = Object::cast_to<WindowWrapper>(node);
			if (restore_window_on_load && floating_docks_dump.has(name)) {
				_restore_floating_dock(floating_docks_dump[name], node, i);
			} else if (wrapper) {
				_dock_floating_close_request(wrapper);
			}
		}
		if (!p_layout->has_section_key(p_section, "dock_" + itos(i + 1) + "_selected_tab_idx")) {
			continue;
		}
		int selected_tab_idx = p_layout->get_value(p_section, "dock_" + itos(i + 1) + "_selected_tab_idx");
		if (selected_tab_idx >= 0 && selected_tab_idx < dock_slot[i]->get_tab_count()) {
			dock_slot[i]->call_deferred("set_current_tab", selected_tab_idx);
		}
	}
	for (int i = 0; i < vsplits.size(); i++) {
		if (!p_layout->has_section_key(p_section, "dock_split_" + itos(i + 1))) {
			continue;
		}
		int ofs = p_layout->get_value(p_section, "dock_split_" + itos(i + 1));
		vsplits[i]->set_split_offset(ofs);
	}
	for (int i = 0; i < hsplits.size(); i++) {
		if (!p_layout->has_section_key(p_section, "dock_hsplit_" + itos(i + 1))) {
			continue;
		}
		int ofs = p_layout->get_value(p_section, "dock_hsplit_" + itos(i + 1));
		hsplits[i]->set_split_offset(ofs);