What might cause my "User error" in Watchdog? I'm trying to figure out the reason behind this "User error" in watchdog

User error: "0" is an invalid render array key in Drupal\Core\Render\Element::children() (line 102 of /core/lib/Drupal/Core/Render/Element.php).


This error comes when I access any non-existing entity like

myentity/762574527 or myentity/anything

On googling, I got this link , which states its due to Token module.

I uninstalled this module and deleted every content related to it, still this error persists. 

Can anyone tell the reason behind this error?
This is not connected to the Token module.

You should not try to render a non existing entity. Your code should throw an exception instead:

use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;

  throw new NotFoundHttpException();


Or configure the route so that when you have a non existing entity as parameter in the route, drupal will throw this exception automatically. See the answer from Berdir to your last question:

https://drupal.stackexchange.com/a/205054/47547