[Console] Fixed symfony#29835: ConfirmationQuestion with default true…

… for answer '0'

When using the ConfirmationQuestion class to ask a yes / no question,
if the default is true, and the answer regex is '/^y/i', then any
value not starting with [yY] is considered false.
This must include "0"

src/Symfony/Component/Console/Question/ConfirmationQuestion.php

@@ -53,7 +53,7 @@ private function getDefaultNormalizer()
                 return $answer && $answerIsTrue;
             }
 
-            return !$answer || $answerIsTrue;
+            return '' === $answer || $answerIsTrue;
         };
     }
 }

src/Symfony/Component/Console/Tests/Question/ConfirmationQuestionTest.php

@@ -41,7 +41,7 @@ public function normalizerUsecases()
             ],
             [
                 true,
-                ['n', 'N', 'no', 'NO', 'nO', 'foo', '1'],
+                ['n', 'N', 'no', 'NO', 'nO', 'foo', '1', '0'],
                 false,
                 'When default is true, the normalizer must return false for "%s"',
             ],