fix escaping strategy that is an array but not a callable

lib/Twig/Extension/Escaper.php

@@ -12,6 +12,13 @@ class Twig_Extension_Escaper extends Twig_Extension
 {
     protected $defaultStrategy;
 
+    /**
+     * Constructor.
+     *
+     * @param string|false|callable $defaultStrategy An escaping strategy
+     *
+     * @see setDefaultStrategy()
+     */
     public function __construct($defaultStrategy = 'html')
     {
         $this->setDefaultStrategy($defaultStrategy);
@@ -55,7 +62,7 @@ class Twig_Extension_Escaper extends Twig_Extension
      * The strategy can be a valid PHP callback that takes the template
      * "filename" as an argument and returns the strategy to use.
      *
-     * @param mixed $defaultStrategy An escaping strategy
+     * @param string|false|callable $defaultStrategy An escaping strategy
      */
     public function setDefaultStrategy($defaultStrategy)
     {
@@ -78,13 +85,13 @@ class Twig_Extension_Escaper extends Twig_Extension
      *
      * @param string $filename The template "filename"
      *
-     * @return string The default strategy to use for the template
+     * @return string|false The default strategy to use for the template
      */
     public function getDefaultStrategy($filename)
     {
         // disable string callables to avoid calling a function named html or js,
         // or any other upcoming escaping strategy
-        if (!is_string($this->defaultStrategy) && is_callable($this->defaultStrategy)) {
+        if (!is_string($this->defaultStrategy) && false !== $this->defaultStrategy) {
             return call_user_func($this->defaultStrategy, $filename);
         }