### 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
immediate_dialog_confirmed = true;
}
bool EditorNode::immediate_confirmation_dialog(const String &p_text, const String &p_ok_text, const String &p_cancel_text) {
	ConfirmationDialog *cd = memnew(ConfirmationDialog);
	cd->set_text(p_text);
	cd->set_ok_button_text(p_ok_text);
	cd->set_cancel_button_text(p_cancel_text);
	cd->connect("confirmed", callable_mp(singleton, &EditorNode::_immediate_dialog_confirmed));
	singleton->gui_base->add_child(cd);
	cd->popup_centered();
	while (true) {
		OS::get_singleton()->delay_usec(1);
		DisplayServer::get_singleton()->process_events();
		Main::iteration();
		if (singleton->immediate_dialog_confirmed || !cd->is_visible()) {
			break;
		}
	}
	memdelete(cd);
	return singleton->immediate_dialog_confirmed;
}
void EditorNode::cleanup() {
	_init_callbacks.clear();
}
int EditorNode::get_current_tab() {
	return scene_tabs->get_current_tab();
}
void EditorNode::set_current_tab(int p_tab) {