Description of the Issue

Specific wrong regex [a-é cause Notepad++ to crash

Steps to Reproduce the Issue

1. Open search dialog and search for [a-é
2. Enable Regular Expression search mode
3. Press Find Next

Expected Behavior

Error message about wrong regex (missing ])

Actual Behavior

Close Notepad++

Debug Information

Notepad++ v8.1.9 (64-bit)
Build time : Oct 21 2021 - 23:37:53
Path : C:\src\npp.8.1.9.portable.x64\notepad++.exe
Command Line :
Admin mode : OFF
Local Conf mode : ON
Cloud Config : OFF
OS Name : Windows 10 Home (64-bit)
OS Version : 2009
OS Build : 19043.1348
Current ANSI codepage : 1252
Plugins : mimeTools.dll NppConverter.dll NppExport.dll