Description of the Issue

The functions list's expanded sub functions collapse when unsorting a sorted function list. The gif below demonstrates the problem

Steps to Reproduce the Issue

1. Open a file along with the function list pane, make sure the function list has toggleable dropdowns
2. expand the dropdowns.
3. Click the sort button twice (Sort and then unsort)

Expected Behavior

retain the expanded state of the sub functions in the function list after the 2nd sort button click

Actual Behavior

function list's sub expanded functions collapse after the 2nd sort button click

Debug Information

Notepad++ v8.1.2 (64-bit)
Build time : Jul 16 2021 - 01:59:50
Path : C:\Users\ASHFAAQ\Downloads\npp.8.1.2.portable.x64\notepad++.exe
Command Line :
Admin mode : OFF
Local Conf mode : ON
Cloud Config : OFF
OS Name : Windows 10 Pro (64-bit)
OS Version : 2009
OS Build : 19042.1110
Current ANSI codepage : 1252
Plugins : mimeTools.dll NppConverter.dll NppExport.dll