### 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
int scene_idx = -1;
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == p_path) {
			scene_idx = i;
			break;
		}
	}
	int current_tab = editor_data.get_edited_scene();
	if (scene_idx == -1) {
		if (get_edited_scene()) {
			
			EditorUndoRedoManager::get_singleton()->clear_history(false, editor_data.get_current_edited_scene_history_id());
		}
		return;
	}
	if (current_tab == scene_idx) {
		editor_data.apply_changes_in_editors();
		_save_editor_states(p_path);
	}
	
	_remove_scene(scene_idx, false);
	load_scene(p_path, true, false, true, true);
	
	editor_data.move_edited_scene_to_index(scene_idx);
	EditorUndoRedoManager::get_singleton()->clear_history(false, editor_data.get_scene_history_id(scene_idx));
	
	scene_tabs->set_current_tab(current_tab);
}
void EditorNode::find_all_instances_inheriting_path_in_node(Node *p_root, Node *p_node, const String &p_instance_path, List<Node *> &p_instance_list) {