All the testing data is out of date. It is not shipped with Joomla. There is already an open issue for it #25777

Please close

No I will not close this one as this is a PHP error, I'll try and replicate it another way, but ANYWAY Joomla should not be returning a PHP error.

Valid bug regardless of whether a reproducer can be supplied, in this case "just read the code" is the right answer.

https://github.com/joomla/joomla-cms/blob/4.0-dev/libraries/src/Application/SiteApplication.php#L173 calls the registry's addExtensionRegistryFile method, which expects a string value and does not support null. Through a series of questionable defaults, it is possible for $component to be null, which can trigger this error. Why $component is null in the request at this point (hard to say what point it's at without a stack trace) is concerning though.

The link points to a non-existing menu item. In J3 a 404 with Component not found message is thrown.

well, that obviously a broken link index.php?Itemid=243
there should be 404 error,
I will do pull later to handle empty $component while addExtensionRegistryFile()

The call to addExtensionRegistryFile() should be wrapped in $component check instead. But, realistically, shouldn't the registry file be added when booting the component?

shouldn't the registry file be added when booting the component?

Need to keep order:
1 component registry file
2 template registry file

So template can override component assets.

hm, or maybe a good idea.

Split this code to 2 parts:
addExtensionRegistryFile($component) move to component booting
addTemplateRegistryFile($template->template, $this->getClientId()) move to $app->render() or something

I try to check

please test #29530

About my previous comment, about "Split this code to 2 parts":
I just remembered that I made in in this way to allow for plugins to do fancy stuff onBeforeRenderEvent