### 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
_find_and_save_edited_subresources(scene, processed, flags);
	for (int i = 0; i < scene->get_child_count(); i++) {
		Node *n = scene->get_child(i);
		if (n->get_owner() != editor_data.get_edited_scene_root()) {
			continue;
		}
		_save_edited_subresources(n, processed, flags);
	}
}
void EditorNode::_find_node_types(Node *p_node, int &count_2d, int &count_3d) {
	if (p_node->is_class("Viewport") || (p_node != editor_data.get_edited_scene_root() && p_node->get_owner() != editor_data.get_edited_scene_root())) {
		return;
	}
	if (p_node->is_class("CanvasItem")) {
		count_2d++;
	} else if (p_node->is_class("Node3D")) {
		count_3d++;
	}
	for (int i = 0; i < p_node->get_child_count(); i++) {
		_find_node_types(p_node->get_child(i), count_2d, count_3d);
	}
}
void EditorNode::_save_scene_with_preview(String p_file, int p_idx) {