I have tested this item unsuccessfully on ae2c056

After applying the patch and going to the link /administrator/index.php?option=com_installer again following error appears

Parse error: syntax error, unexpected '<' in C:\xampp\htdocs\stagingtest\administrator\components\com_installer\views\install\tmpl\default.php on line 108
Call Stack

Time Memory Function Location

1 0.0013 139600 {main}( ) ..\index.php:0
2 0.1304 2593880 JApplicationCms->execute( ) ..\index.php:51
3 0.1304 2594032 JApplicationAdministrator->doExecute( ) ..\cms.php:257
4 0.1946 3917776 JApplicationAdministrator->dispatch( ) ..\administrator.php:152
5 0.2109 4162304 JComponentHelper::renderComponent( ) ..\administrator.php:98
6 0.2140 4210688 JComponentHelper::executeComponent( ) ..\helper.php:380
7 0.2143 4232064 require_once( 'C:\xampp\htdocs\stagingtest\administrator\components\com_installer\installer.php' ) ..\helper.php:405
8 0.2397 4831416 JControllerLegacy->execute( ) ..\installer.php:19
9 0.2397 4831536 InstallerController->display( ) ..\legacy.php:728
10 0.2652 5303544 InstallerViewInstall->display( ) ..\controller.php:59
11 0.2676 5304848 InstallerViewDefault->display( ) ..\view.html.php:46
12 0.3018 5548464 JViewLegacy->display( ) ..\view.php:62
13 0.3018 5548720 JViewLegacy->loadTemplate( ) ..\legacy.php:209

This PR has received new commits.

CC: @shubhamnba2009

Fixed : added the missing ?>

Getting these error on checking the source file of /administrator/index.php?option=com_installer at https://validator.w3.org after applying the patch.

Error: Attribute type not allowed on element div at this point.
From line 423, column 3; to line 429, column 2
apper">↩ ↩ Attributes for element div:
Global attributes
Warning: Section lacks heading. Consider using h2-h6 elements to add identifying headings to all sections.
From line 409, column 2; to line 409, column 23
r-main">↩

Please note that fixe concerns only one of the errors on all W3C compliance errors which previsouly exist on the page (you can compare with and without the fixe). The 2 pending error are from the menu, I think, and are existing on most of pages (components) on the backend.

I have tested this item successfully on 55ceb24

Removes Error : Error: Element style not allowed as child of element div in this context" (From line 431, column 11; to line 431) as per https://validator.w3.org validator.

I have tested this item successfully on 55ceb24

BTW the other error comes from here https://github.com/joomla/joomla-cms/blob/staging/layouts/joomla/sidebars/toggle.php

Merged - thanks!