### 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
switch (tool_menu->get_item_id(p_idx)) {
		case TOOLS_ORPHAN_RESOURCES: {
			orphan_resources->show();
		} break;
		case TOOLS_CUSTOM: {
			if (tool_menu->get_item_submenu(p_idx) == "") {
				Callable callback = tool_menu->get_item_metadata(p_idx);
				Callable::CallError ce;
				Variant result;
				callback.callp(nullptr, 0, result, ce);
				if (ce.error != Callable::CallError::CALL_OK) {
					String err = Variant::get_callable_error_text(callback, nullptr, 0, ce);
					ERR_PRINT("Error calling function from tool menu: " + err);
				}
			} 
		} break;
	}
}
void EditorNode::_export_as_menu_option(int p_idx) {