DarkModeDefault.xml become very eavy.

[SigmaFlame]

Description of the Issue

Hello,
When Notepad++ is used for a very long time, it become slow to open a file. It could take some seconds.
This issue seems to be caused by the file DarkModeDefault.xml that become very eavy. (64 Mo in my case)

Steps to Reproduce the Issue

Using the program for a very long time, multiple weeks or years, updating it when asked, and so on.

Expected Behavior

It stays fast.

Actual Behavior

It becomes slow after a while, some weeks or years after, depending of the usage.

Debug Information

According to my tests, it appears that the file « %appdata%/Notepad++/themes/DarkModeDefault.xml » become very eavy.
Deleting this file makes the program fast again, the dark mode is still on and this file is not automatically recreated.
Deleting all « %appdata%/Notepad++ » recreate a new light DarkModeDefault.xml file.

My old DarkModeDefault.xml have a size of 64.1 Mo with 67 292 488 lines. The default one is only 183 Ko.
This file is very too eavy to be opened with any program that I have on my computer.
I guess at some time, something went wrong somewhere and this file will increase its size each time I open a file.

On my Notepadd++ settings I have disabled "memory session" so if I close the program with files open, they are closed the next time I open Notepad++, and I added some word in the PHP colorization section.

[mpheath]

It appears an accented character triggered this corruption to occur.

The top line is fresh from v8.5.4 portable zip.
The bottom line is from v8.5.4 in use which shows some corruption and probably gets larger over time.

The latest version does not have the accented character in the comment header.

notepad-plus-plus/PowerEditor/installer/themes/DarkModeDefault.xml

Lines 2 to 6 in 12548b6

	<!--
	Dark mode default style for Notepad++.
	This file is based on Zenburn them (zenburn.xml)
	License: GPL2
	-->