### 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.
right_hsplit->add_child(right_l_vsplit);
	dock_slot[DOCK_SLOT_RIGHT_UL] = memnew(TabContainer);
	right_l_vsplit->add_child(dock_slot[DOCK_SLOT_RIGHT_UL]);
	dock_slot[DOCK_SLOT_RIGHT_BL] = memnew(TabContainer);
	right_l_vsplit->add_child(dock_slot[DOCK_SLOT_RIGHT_BL]);
	right_r_vsplit = memnew(VSplitContainer);
	right_hsplit->add_child(right_r_vsplit);
	dock_slot[DOCK_SLOT_RIGHT_UR] = memnew(TabContainer);
	right_r_vsplit->add_child(dock_slot[DOCK_SLOT_RIGHT_UR]);
	dock_slot[DOCK_SLOT_RIGHT_BR] = memnew(TabContainer);
	right_r_vsplit->add_child(dock_slot[DOCK_SLOT_RIGHT_BR]);
	
	vsplits.push_back(left_l_vsplit);
	vsplits.push_back(left_r_vsplit);
	vsplits.push_back(right_l_vsplit);
	vsplits.push_back(right_r_vsplit);
	hsplits.push_back(left_l_hsplit);
	hsplits.push_back(left_r_hsplit);
	hsplits.push_back(main_hsplit);
	hsplits.push_back(right_hsplit);
	for (int i = 0; i < vsplits.size(); i++) {
		vsplits[i]->connect("dragged", callable_mp(this, &EditorNode::_dock_split_dragged));
		hsplits[i]->connect("dragged", callable_mp(this, &EditorNode::_dock_split_dragged));
	}
	dock_select_popup = memnew(PopupPanel);
	gui_base->add_child(dock_select_popup);
	VBoxContainer *dock_vb = memnew(VBoxContainer);
	dock_select_popup->add_child(dock_vb);
	HBoxContainer *dock_hb = memnew(HBoxContainer);
	dock_tab_move_left = memnew(Button);