### 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
List<Node *> nodes_owned_by_original_node;
				original_node->get_owned_by(original_node, &nodes_owned_by_original_node);
				for (Node *owned_node : nodes_owned_by_original_node) {
					owned_node->set_owner(nullptr);
				}
				
				while (original_node->get_child_count()) {
					Node *child = original_node->get_child(0);
					original_node->remove_child(child);
					child->queue_free();
				}
				
				bool is_editable = true;
				Node *owner = original_node->get_owner();
				if (owner) {
					is_editable = owner->is_editable_instance(original_node);
				}
				
				Ref<PackedScene> current_packed_scene;
				if (original_node->get_scene_file_path() == p_instance_path) {
					
					
					current_packed_scene = instance_scene_packed_scene;
				} else {
					
					
					List<String> required_load_paths;
					String scene_path = original_node->get_scene_file_path();