### 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
bottom_panel_updating = true;
		for (int i = 0; i < bottom_panel_items.size(); i++) {
			bottom_panel_items[i].button->set_pressed(i == p_idx);
			bottom_panel_items[i].control->set_visible(i == p_idx);
		}
		if (EditorDebuggerNode::get_singleton() == bottom_panel_items[p_idx].control) {
			
			bottom_panel->add_theme_style_override("panel", gui_base->get_theme_stylebox(SNAME("BottomPanelDebuggerOverride"), SNAME("EditorStyles")));
		} else {
			bottom_panel->add_theme_style_override("panel", gui_base->get_theme_stylebox(SNAME("BottomPanel"), SNAME("EditorStyles")));
		}
		center_split->set_dragger_visibility(SplitContainer::DRAGGER_VISIBLE);
		center_split->set_collapsed(false);
		if (bottom_panel_raise->is_pressed()) {
			top_split->hide();
		}
		bottom_panel_raise->show();
	} else {
		bottom_panel->add_theme_style_override("panel", gui_base->get_theme_stylebox(SNAME("BottomPanel"), SNAME("EditorStyles")));
		bottom_panel_items[p_idx].button->set_pressed(false);
		bottom_panel_items[p_idx].control->set_visible(false);
		center_split->set_dragger_visibility(SplitContainer::DRAGGER_HIDDEN);
		center_split->set_collapsed(true);
		bottom_panel_raise->hide();
		if (bottom_panel_raise->is_pressed()) {
			top_split->show();
		}
	}
}
void EditorNode::set_docks_visible(bool p_show) {