SOLVED Can't see pages trough error

[Troost]

Hi all!

At first, i want to wish everybody happy 2020, with a lot of creativity, beautiful projects and lots of fun!

I've a website for a client with an admin account (my acc) and a user account (for the client).
Everything works fine for me, but when the client tries to login, i've got the following popup / error:

        Method ProcessPageListRenderJSON::getUseTrash does not exist or is not callable in this context

When I press OK, nothing happens, so the admin panel is empty for the client. 
I've tried to figure it out with some premissions on the users/roles page, but this won't work out either.

See attached screenshots from the error messages, the 'admin' side and the 'client' side.

Can someone help us out?
Thanks in advance!

[dragan]

Did you change anything lately? Installed new modules? Hooks? Install Tracy Debugger and see if it tells you more.

[Troost]

Thanks Dragan, I haven't changed anything lately. Ill try if Tracy Debugger will tell me something.

[dragan]

Perhaps it's this issue? https://github.com/processwire/processwire-issues/issues/817

I just noticed you're running the same PW version as the OP in that issue report.

[Troost]

Thanks @dragan

That looks like my issue as well, I will have a look on this in a few days, when I manage to fix it, ill let you know!
 

[Troost]

@Dragan, I commented some lines out in the ProcessPageListRenderJSON.php which made the pages visible.

if(!$this->superuser && $page404 && $page404->parent_id == 1 && !isset($extraPages[$idTrash])) {
	$pageTrash = $this->wire('pages')->get($idTrash);
	if($pageTrash->id && $this->getUseTrash() && $pageTrash->listable()) {
		$extraPages[$pageTrash->id] = $pageTrash;
	}
}

Thanks