Pull Request for Issue #36669 .

Summary of Changes

Remove JPATH_ROOT from absolute file path only if JPATH_ROOT is at beginning of string

Testing Instructions

Added by rdeutz

• Find out the root path of your installation e.g /var/www/joomla
• create a directory /var/www/joomla/media/templates/site/cassiopeia/images/var/www/joomla and copy an image file into the directory e.g. myimage.png
• go into the template index.php
• add echo HTMLHelper::_('image', 'var/www/joomla/myimage.png', 'theImage', [], true,0);

Actual result BEFORE applying this Pull Request

If JPATH_ROOT is repeated inside file names, resources are not getting loaded.

Example:
JPATH_ROOT = '/joomla'
$path = '/joomla/media/system/images/joomla-favicon.svg'
Wrong output before: /media/system/images-favicon.svg

Another less unusual example:
JPATH_ROOT = '/app/html
$path = '/app/html/media/com_something/js/app/html_custom.js'
Wrong output before: /media/com_something/js_custom.js

Expected result AFTER applying this Pull Request

If JPATH_ROOT is present 2 times in the $path, it will be removed only if at beginning (where it should be)

Example:
JPATH_ROOT = '/joomla'
$path = '/joomla/media/system/images/joomla-favicon.svg'
Correct output with patch: /media/system/images/joomla-favicon.svg

Another less unusual example:
JPATH_ROOT = '/app/html
$path = '/app/html/media/com_something/js/app/html_custom.js'
Wrong output before: /media/com_something/js/app/html_custom.js

Documentation Changes Required

Problem was not declared anywhere else

Code run as before (JPATH_ROOT is not supposed to be in the middle of the $path if not for casuality)