### 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
ERR_FAIL_COND(!instantiated_node);
				bool original_node_is_displayed_folded = original_node->is_displayed_folded();
				bool original_node_scene_instance_load_placeholder = original_node->get_scene_instance_load_placeholder();
				
				instantiated_node->set_name(original_node->get_name());
				
				String original_node_file_path = original_node->get_scene_file_path();
				if (current_edited_scene == original_node) {
					instantiated_node->set_scene_instance_state(original_node->get_scene_instance_state());
					
					if (original_node_file_path.is_empty()) {
						Ref<SceneState> state = current_packed_scene->get_state();
						state->set_path(current_packed_scene->get_path());
						instantiated_node->set_scene_inherited_state(state);
						instantiated_node->set_scene_file_path(String());
					}
					editor_data.set_edited_scene_root(instantiated_node);
					current_edited_scene = instantiated_node;
					if (original_node->is_inside_tree()) {
						SceneTreeDock::get_singleton()->set_edited_scene(current_edited_scene);
						original_node->get_tree()->set_edited_scene_root(instantiated_node);
					}
				}
				
				original_node->replace_by(instantiated_node, false);
				
				original_node->queue_free();
				
				instantiated_node->set_display_folded(original_node_is_displayed_folded);
				instantiated_node->set_scene_instance_load_placeholder(original_node_scene_instance_load_placeholder);