### 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
Ref<Script> scr = editor_data.get_scene_root_script(p_tab);
	if (scr.is_valid()) {
		InspectorDock::get_singleton()->edit_resource(scr);
	}
}
void EditorNode::_proceed_closing_scene_tabs() {
	List<String>::Element *E = tabs_to_close.front();
	if (!E) {
		if (_is_closing_editor()) {
			current_menu_option = tab_closing_menu_option;
			_menu_option_confirm(tab_closing_menu_option, true);
		} else {
			current_menu_option = -1;
			save_confirmation->hide();
		}
		return;
	}
	String scene_to_close = E->get();
	tabs_to_close.pop_front();
	int tab_idx = -1;
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == scene_to_close) {
			tab_idx = i;
			break;
		}
	}
	ERR_FAIL_COND(tab_idx < 0);
	_scene_tab_closed(tab_idx);
}
bool EditorNode::_is_closing_editor() const {