Error after upgrading from Joomla 4 to Joomla 5

facilitairrtv

I have problems with all the T4 Templates even the tpl_t4_bs5_blank_1.2.5 template.

I get the following error:
Error Code: Joomla\CMS\Event\Module\ModuleListEvent::onSetModules(): Argument #1 ($value) must be of type array, null given, called in /var/www/somesite/web/libraries/src/Event/AbstractEvent.php on line 227

I have created a clone of the website and that address is available for testing.

I already tried:
Disabling all modules
Disabling menu items
Disabling plugins

Tried different versions of MySQL and Nginx but also didn't fix the issue.

I Tried different suggestions from the community with renaming file names and editing directory names.

If someone has an answer please let me know. It already cost me more then 10+ hours to try to get past this error.

saguaros

facilitairrtv Hi

You have lots of modules enabled now, could you temporarily disable all of them first?

facilitairrtv

saguaros

Like I said in my original message. I have disabled all the modules and started all over again. But even with all the modules disabled the message still continues to appear. So that didn't solve the issue. Also disabling the modules before the update and then updating still resulted in the same issue.

You're allowed to make changes within the website. If you would give it a try. There is a snapshot so I can place the machine back in time. When we found the issue or when the site got broken.

facilitairrtv

I have found an error message in the PHP log:
[05-Feb-2026 21:39:00 UTC] PHP Deprecated: T4\MVC\Router\T4::__construct(): Implicitly marking parameter $app as nullable is deprecated, the explicit nullable type must be used instead in /var/www/somesite/web/plugins/system/t4/src/t4/MVC/Router/T4.php on line 82

[05-Feb-2026 21:39:00 UTC] PHP Deprecated: T4\MVC\Router\T4::__construct(): Implicitly marking parameter $menu as nullable is deprecated, the explicit nullable type must be used instead in /var/www/somesite/web/plugins/system/t4/src/t4/MVC/Router/T4.php on line 82

This Article does mention this issue

facilitairrtv

This problem seems to have occurred once before.
Link to Forum post

I tried the change muratyil suggested. This removed the PHP error from the log. But it did not fix the issue.

facilitairrtv

It has been resolved by the template creator. Who build this template based on T4.

The problem was based on the issue mentioned in This forum post

I did this earlier but in place of renaming/deleting the file I made a copy of the file. This does not work you really have to delete/rename the file.