### 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
}
		InspectorDock::get_inspector_singleton()->edit(current_obj);
		NodeDock::get_singleton()->set_node(nullptr);
		SceneTreeDock::get_singleton()->set_selected(selected_node);
		InspectorDock::get_singleton()->update(nullptr);
	}
	if (current_obj == prev_inspected_object) {
		
		InspectorDock::get_inspector_singleton()->update_tree();
	}
	InspectorDock::get_singleton()->set_info(
			info_is_warning ? TTR("Changes may be lost!") : TTR("This object is read-only."),
			editable_info,
			info_is_warning);
	if (InspectorDock::get_inspector_singleton()->is_using_folding() == disable_folding) {
		InspectorDock::get_inspector_singleton()->set_use_folding(!disable_folding);
	}
	Object *editor_owner = is_node ? (Object *)SceneTreeDock::get_singleton() : is_resource ? (Object *)InspectorDock::get_inspector_singleton()
																							: (Object *)this;
	
	if (!inspector_only) {
		EditorPlugin *main_plugin = editor_data.get_editor(current_obj);
		int plugin_index = 0;
		for (; plugin_index < editor_table.size(); plugin_index++) {
			if (editor_table[plugin_index] == main_plugin) {
				if (!main_editor_buttons[plugin_index]->is_visible()) {
					main_plugin = nullptr; 
				}
				break;
			}