Merge branch '3.4' into 4.2

* 3.4:
  SCA: minor code tweaks
  [Intl] Update the ICU data to 64.1
  [Bridge][Twig] DebugCommand - fix escaping and filter

Author: nicolas-grekas

Tester/TesterTrait.php

@@ -35,6 +35,10 @@ trait TesterTrait
      */
     public function getDisplay($normalize = false)
     {
+        if (null === $this->output) {
+            throw new \RuntimeException('Output not initialized, did you execute the command before requesting the display?');
+        }
+
         rewind($this->output->getStream());
 
         $display = stream_get_contents($this->output->getStream());