### 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
valid_source_owner = valid_source_owner->get_owner();
				}
			}
			if (!source_node || valid_source_owner == nullptr) {
				
				if (!c.callable.is_custom()) {
					valid_connections_from.push_back(c);
				}
			}
		}
		
		List<Node::GroupInfo> groups;
		p_node->get_groups(&groups);
		if (!modified_properties.is_empty() || !valid_connections_to.is_empty() || !valid_connections_from.is_empty() || !groups.is_empty()) {
			ModificationNodeEntry modification_node_entry;
			modification_node_entry.property_table = modified_properties;
			modification_node_entry.connections_to = valid_connections_to;
			modification_node_entry.connections_from = valid_connections_from;
			modification_node_entry.groups = groups;
			p_modification_table[p_root->get_path_to(p_node)] = modification_node_entry;
		}
	} else {
		AdditiveNodeEntry new_additive_node_entry;
		new_additive_node_entry.node = p_node;
		new_additive_node_entry.parent = p_root->get_path_to(p_node->get_parent());
		new_additive_node_entry.owner = p_node->get_owner();
		new_additive_node_entry.index = p_node->get_index();
		Node2D *node_2d = Object::cast_to<Node2D>(p_node);
		if (node_2d) {
			new_additive_node_entry.transform_2d = node_2d->get_relative_transform_to_parent(node_2d->get_parent());