Update to Drupal 8.2.0. For more information, see https://www.drupal.org/project/drupal/releases/8.2.0

core/lib/Drupal/Core/Template/TwigExtension.php

@@ -573,7 +573,7 @@ class TwigExtension extends \Twig_Extension {
    *
    * @param \Twig_Environment $env
    *   A Twig_Environment instance.
-   * @param mixed[]|\Traversable|NULL $value
+   * @param mixed[]|\Traversable|null $value
    *   The pieces to join.
    * @param string $glue
    *   The delimiter with which to join the string. Defaults to an empty string.

core/lib/Drupal/Core/Template/TwigNodeTrans.php

@@ -169,6 +169,9 @@ class TwigNodeTrans extends \Twig_Node {
         }
       }
     }
+    elseif (!$body->hasAttribute('data')) {
+      throw new \Twig_Error_Syntax('{% trans %} tag cannot be empty');
+    }
     else {
       $text = $body->getAttribute('data');
     }