i can confirm, even if it is not a fatal error but a Notice ?

Oops, didn't even read the notice....just saw an orange box lol

This gets rid of the Notice

		foreach ($rows as $extension)
		{
			if ($extension->manifest_cache)
			{
				$decode = json_decode($extension->manifest_cache);
				$this->translateExtensionName($extension);
				$extension->version = $decode->version;
				unset($extension->manifest_cache);
			}
		}

But it rather looks like a hack. :)

This notice happens when the extensions updater wants to check for an extension if there is an update, and this extension is a core extension but not added to the ExtensioneHelper.php core extensions list, so the updater tries to find an update like for 3rd party extensions. I will try to find out which extension is missing and if I find it, I will make a PR.

I've once noticed that here bembelimen#37 (comment) and solved it here bembelimen#39. Is the same file and same line where the warning occurs.

I think I have found it, but it seems not to come from the new backend template, i.e. the notice should have been there before, too.

@wilsonge The testing sample data is missing in the list of core extensions in the ExtensionHelper.php. But testing sample data is only available when working on cloned git repo, not when using e.g. a nightly build or a release package. That's why I did not get the notice when testing with the backend template, it was a nightly build. Do you know if it is safe then to add it to the list? If we don't add it we get the PHP notice mentioned above when it is available. But what happens if I add it and it is not available?

Yeah, that was it, testing sample data missing in core extensions list. If fixed, notice goes away.

PR is on the way.

Dont forget that testing sample daata plugin will not be shipped with joomla

@brianteeman Read my question to George above and you will see that I am pretty much aware of it. But it needs to be in the list if present. Question is if it will do harm when in the list but not present.

@brianteeman I've just checked, it is safe to have something which is not shipped in the list of core extensions, because this list is used to build where clauses for database queries, and if that thing is not installed, it will not be in the result set of that query because it is not in the extensions table in database.
@wilsonge No need for you to help, I've got it.

Closed as having Pull Request #25910

@brianteeman Would be nice if you can find time for testing. We currently have a lack of testers, maybe due to holidays.

New Pull Request is #25919 . Please test.