### 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
String distribution_name = OS::get_singleton()->get_distribution_name();
	if (distribution_name.is_empty()) {
		distribution_name = OS::get_singleton()->get_name();
	}
	if (distribution_name.is_empty()) {
		distribution_name = "Other";
	}
	const String distribution_version = OS::get_singleton()->get_version();
	String godot_version = "Godot v" + String(VERSION_FULL_CONFIG);
	if (String(VERSION_BUILD) != "official") {
		String hash = String(VERSION_HASH);
		hash = hash.is_empty() ? String("unknown") : vformat("(%s)", hash.left(9));
		godot_version += " " + hash;
	}
#ifdef LINUXBSD_ENABLED
	const String display_server = OS::get_singleton()->get_environment("XDG_SESSION_TYPE").capitalize().replace(" ", ""); 
#endif 
	String driver_name = GLOBAL_GET("rendering/rendering_device/driver");
	String rendering_method = GLOBAL_GET("rendering/renderer/rendering_method");
	const String rendering_device_name = RenderingServer::get_singleton()->get_video_adapter_name();
	RenderingDevice::DeviceType device_type = RenderingServer::get_singleton()->get_video_adapter_type();
	String device_type_string;
	switch (device_type) {
		case RenderingDevice::DeviceType::DEVICE_TYPE_INTEGRATED_GPU:
			device_type_string = "integrated";
			break;
		case RenderingDevice::DeviceType::DEVICE_TYPE_DISCRETE_GPU:
			device_type_string = "dedicated";
			break;