### Godot version

v4.2.dev.custom_build [0c2144da9]

### System information

Debian Linux X11 Xfce

### Issue description

Prerequisite: Be in Single Window Mode in the Editor
The Filesystem Dock is unusable when it is floating, which is not expected.
It appears garbled in the top-left corner:
![image](https://github.com/godotengine/godot/assets/6299227/109f7922-97de-44c3-814a-ca7f970e0602)

The following errors are shown:
```
  editor/window_wrapper.cpp:220 - Condition "!is_window_available()" is true.
  editor/window_wrapper.cpp:202 - Condition "!get_window_enabled()" is true. Returning: Rect2i()
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
```

bisecting lead to #62378
possibly related to #44439

### Steps to reproduce

1. Start a project in the Editor
2. Switch to Single Window Mode in the Editor and reload (if necessary)
3. Make the Filesystem Dock floating

### Minimal reproduction project

Editor issue
distraction_free->set_pressed(p_enter);
	if (p_enter) {
		if (docks_visible) {
			set_docks_visible(false);
		}
	} else {
		set_docks_visible(true);
	}
}
bool EditorNode::is_distraction_free_mode_enabled() const {
	return distraction_free->is_pressed();
}
void EditorNode::add_control_to_dock(DockSlot p_slot, Control *p_control) {
	ERR_FAIL_INDEX(p_slot, DOCK_SLOT_MAX);
	dock_slot[p_slot]->add_child(p_control);
	_update_dock_slots_visibility();
}
void EditorNode::remove_control_from_dock(Control *p_control) {