Pull Request followup #48127.

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

#48127 introduced a new security flag for updates. The limitation was, when a never update has no security issue, it will not flag the update accordingly, see this comment. This pr fixes that. The severity is now shown from the highest update since the currently installed version. See testing instructions for example:

Testing Instructions

The update site is modified now with the following updates:

• Version 0.9.0 -> severity 4 (Critical)
• Version 1.0.0 -> severity null (no information)
• Version 1.0.1 -> severity 3 (High)
• Version 1.0.2 -> severity 2 (Medium)
  The file to download has version 1.0.0 with no severity.

• Install the module mod_demo.zip
• Open the page /administrator/index.php?option=com_installer&view=update
• Click on "Check for updates"

Actual result BEFORE applying this Pull Request

Update is shown with security Medium.

Expected result AFTER applying this Pull Request

Update is shown with security High.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed