### 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.
unr.size -= Vector2(4, 7);
	dock_select->draw_rect(unr, unusable);
	dock_tab_move_left->set_disabled(true);
	dock_tab_move_right->set_disabled(true);
	if (dock_popup_selected_idx != -1 && dock_slot[dock_popup_selected_idx]->get_tab_count()) {
		dock_tab_move_left->set_disabled(dock_slot[dock_popup_selected_idx]->get_current_tab() == 0);
		dock_tab_move_right->set_disabled(dock_slot[dock_popup_selected_idx]->get_current_tab() >= dock_slot[dock_popup_selected_idx]->get_tab_count() - 1);
	}
	for (int i = 0; i < DOCK_SLOT_MAX; i++) {
		Vector2 ofs;
		switch (i) {
			case DOCK_SLOT_LEFT_UL: {
			} break;
			case DOCK_SLOT_LEFT_BL: {
				ofs.y += s.y;
			} break;
			case DOCK_SLOT_LEFT_UR: {
				ofs.x += s.x;
			} break;
			case DOCK_SLOT_LEFT_BR: {
				ofs += s;
			} break;
			case DOCK_SLOT_RIGHT_UL: {
				ofs.x += s.x * 4;
			} break;
			case DOCK_SLOT_RIGHT_BL: {
				ofs.x += s.x * 4;
				ofs.y += s.y;
			} break;
			case DOCK_SLOT_RIGHT_UR: {