### 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
vbc->add_child(disk_changed_list);
		disk_changed_list->set_v_size_flags(Control::SIZE_EXPAND_FILL);
		disk_changed->connect("confirmed", callable_mp(this, &EditorNode::_reload_modified_scenes));
		disk_changed->connect("confirmed", callable_mp(this, &EditorNode::_reload_project_settings));
		disk_changed->set_ok_button_text(TTR("Reload"));
		disk_changed->add_button(TTR("Resave"), !DisplayServer::get_singleton()->get_swap_cancel_ok(), "resave");
		disk_changed->connect("custom_action", callable_mp(this, &EditorNode::_resave_scenes));
	}
	gui_base->add_child(disk_changed);
	add_editor_plugin(memnew(AnimationPlayerEditorPlugin));
	add_editor_plugin(memnew(AnimationTrackKeyEditEditorPlugin));
	add_editor_plugin(memnew(CanvasItemEditorPlugin));
	add_editor_plugin(memnew(Node3DEditorPlugin));
	add_editor_plugin(memnew(ScriptEditorPlugin));
	EditorAudioBuses *audio_bus_editor = EditorAudioBuses::register_editor();
	ScriptTextEditor::register_editor(); 
	TextEditor::register_editor();
	if (AssetLibraryEditorPlugin::is_available()) {
		add_editor_plugin(memnew(AssetLibraryEditorPlugin));
	} else {
		print_verbose("Asset Library not available (due to using Web editor, or SSL support disabled).");
	}
	
	raise_bottom_panel_item(AnimationPlayerEditor::get_singleton());
	add_editor_plugin(VersionControlEditorPlugin::get_singleton());
	vcs_actions_menu = VersionControlEditorPlugin::get_singleton()->get_version_control_actions_panel();
	vcs_actions_menu->set_name("Version Control");
	vcs_actions_menu->connect("index_pressed", callable_mp(this, &EditorNode::_version_control_menu_option));
	vcs_actions_menu->add_item(TTR("Create Version Control Metadata"), RUN_VCS_METADATA);
	vcs_actions_menu->add_item(TTR("Version Control Settings"), RUN_VCS_SETTINGS);