### 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
for (int i = 0; i < bottom_panel_items.size(); i++) {
		if (bottom_panel_items[i].control->is_visible()) {
			_bottom_panel_switch(false, i);
			break;
		}
	}
}
void EditorNode::make_bottom_panel_item_visible(Control *p_item) {
	for (int i = 0; i < bottom_panel_items.size(); i++) {
		if (bottom_panel_items[i].control == p_item) {
			_bottom_panel_switch(true, i);
			break;
		}
	}
}
void EditorNode::raise_bottom_panel_item(Control *p_item) {
	for (int i = 0; i < bottom_panel_items.size(); i++) {
		if (bottom_panel_items[i].control == p_item) {
			bottom_panel_items[i].button->move_to_front();
			SWAP(bottom_panel_items.write[i], bottom_panel_items.write[bottom_panel_items.size() - 1]);
			break;
		}
	}
	for (int i = 0; i < bottom_panel_items.size(); i++) {
		bottom_panel_items[i].button->disconnect("toggled", callable_mp(this, &EditorNode::_bottom_panel_switch));
		bottom_panel_items[i].button->connect("toggled", callable_mp(this, &EditorNode::_bottom_panel_switch).bind(i));
	}
}
void EditorNode::remove_bottom_panel_item(Control *p_item) {