Description of the Issue

Typing out a multi-part keyword (enclosed in either single or double quotes) that consists of more than 1 word which has been defined in a group that has prefix mode enabled will freeze Notepad++ and cause it to not respond.

Steps to Reproduce the Issue

1. Create a new file.
2. Set the language to User-Defined. (Language > User-Defined)
3. Open the UDL menu. (Language > User Defined Language > Define your language...)
4. Ensure the User language field is set to User Defined Language.
5. Navigate to the Keywords Lists tab.
6. Enter anything that is enclosed in either double or single quotes that includes at least one space in any group.
   Examples:
   "Hello, world!"
'Example multi-part keyword'
7. Ensure that that group has Prefix mode set.
8. Type out the keyword in the file, followed by a space or a line break.

Expected Behavior

The expected style would be applied to the keyword.

Actual Behavior

Notepad++ freezes.

Debug Information

Notepad++ v8.1.9.3 (64-bit)
Build time : Dec 6 2021 - 19:21:37
Path : C:\Program Files\Notepad++\notepad++.exe
Command Line :
Admin mode : OFF
Local Conf mode : OFF
Cloud Config : OFF
OS Name : Windows 10 Home (64-bit)
OS Version : 2009
OS Build : 19044.1586
Current ANSI codepage : 1250
Plugins : mimeTools.dll NppConverter.dll NppExport.dll

Screenshots