### 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
editable_info = TTR("This resource belongs to a scene that was instantiated or inherited.\nChanges to it must be made inside the original scene.");
					}
				}
			} else {
				if (FileAccess::exists(base_path + ".import")) {
					editable_info = TTR("This resource belongs to a scene that was imported, so it's not editable.\nPlease read the documentation relevant to importing scenes to better understand this workflow.");
				}
			}
		} else if (current_res->get_path().is_resource_file()) {
			if (FileAccess::exists(current_res->get_path() + ".import")) {
				editable_info = TTR("This resource was imported, so it's not editable. Change its settings in the import panel and then re-import.");
			}
		}
	} else if (is_node) {
		Node *current_node = Object::cast_to<Node>(current_obj);
		ERR_FAIL_COND(!current_node);
		InspectorDock::get_inspector_singleton()->edit(current_node);
		if (current_node->is_inside_tree()) {
			NodeDock::get_singleton()->set_node(current_node);
			SceneTreeDock::get_singleton()->set_selected(current_node);
			InspectorDock::get_singleton()->update(current_node);
			if (!inspector_only && !skip_main_plugin) {
				skip_main_plugin = stay_in_script_editor_on_node_selected && ScriptEditor::get_singleton()->is_visible_in_tree();
			}
		} else {
			NodeDock::get_singleton()->set_node(nullptr);
			SceneTreeDock::get_singleton()->set_selected(nullptr);
			InspectorDock::get_singleton()->update(nullptr);
		}
		if (get_edited_scene() && !get_edited_scene()->get_scene_file_path().is_empty()) {