### 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
if (p_editor->has_main_screen()) {
		Button *tb = memnew(Button);
		tb->set_flat(true);
		tb->set_toggle_mode(true);
		tb->connect("pressed", callable_mp(singleton, &EditorNode::editor_select).bind(singleton->main_editor_buttons.size()));
		tb->set_name(p_editor->get_name());
		tb->set_text(p_editor->get_name());
		Ref<Texture2D> icon = p_editor->get_icon();
		if (icon.is_valid()) {
			tb->set_icon(icon);
			
			icon->connect_changed(callable_mp((Control *)tb, &Control::update_minimum_size));
		} else if (singleton->gui_base->has_theme_icon(p_editor->get_name(), SNAME("EditorIcons"))) {
			tb->set_icon(singleton->gui_base->get_theme_icon(p_editor->get_name(), SNAME("EditorIcons")));
		}
		tb->add_theme_font_override("font", singleton->gui_base->get_theme_font(SNAME("main_button_font"), SNAME("EditorFonts")));
		tb->add_theme_font_size_override("font_size", singleton->gui_base->get_theme_font_size(SNAME("main_button_font_size"), SNAME("EditorFonts")));
		singleton->main_editor_buttons.push_back(tb);
		singleton->main_editor_button_hb->add_child(tb);
		singleton->editor_table.push_back(p_editor);
		singleton->distraction_free->move_to_front();
	}
	singleton->editor_data.add_editor_plugin(p_editor);
	singleton->add_child(p_editor);
	if (p_config_changed) {
		p_editor->enable_plugin();
	}
}
void EditorNode::remove_editor_plugin(EditorPlugin *p_editor, bool p_config_changed) {