I'm merging from eZP 4.0.1 to eZP 4.1.0

So, when i click 'Apply changes' in tab Set up / Extensions (/setup/extensions), i lose my custom pagelayout (admin).

I checked this issue is also into an eZP 4.1.0

Steps to reproduce

From a clean eZP 4.1.0

Create a custom_admin design:

Copy /design/admin/templates/pagelayout.tpl
to /design/custom_admin/templates/pagelayout.tpl
Edit /design/custom_admin/templates/pagelayout.tpl and Flag this pagelayout like this
line 109 <p>version

{fetch( setup, version )}

custom</p>

Add the new design custom design folder :
Edit /settings/site_access/<custom_admin>/site.ini.append.php

[DesignSettings]
SiteDesign=custom_admin
AdditionalSiteDesignList[]=admin

[DebugSettings]
DebugOutput=enabled

[TemplateSettings]
ShowUsedTemplates=enabled

Clear all cache

You can read "version 4.1.0 custom"
Go to tab Set up / Extension
Click Apply changes : The pagelayout is lost and default pagelayout is called (you can only read "version 4.1.0"