bug #14654 [Console] SymfonyStyle : fix blocks failed when $messages is null (ogizanagi)

This PR was merged into the 2.7 branch.

Discussion
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[Console] SymfonyStyle : fix blocks failed when $messages is null

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Using `SymfonyStyle:block` method with `null` as first argument failed, where most of other methods accepting both string and array arguments will simply output an empty string.

At first I wanted to output nothing, or even throw a proper exception. But then I realized how behaves other methods like text or write.

I encountered this issue while executing a console application, in non-interactive mode, that asks questions (without default value) and prints the result immediately using a note block:
```php
$output->note($output->choice('Choice question', array('choice 1', 'choice 2'));
```
![screenshot 2015-05-16 a 11 42 47](https://cloud.githubusercontent.com/assets/2211145/7665616/ba5f343c-fbc0-11e4-811d-6b109aaa8d27.PNG)

Commits
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cfd1022 [Console] SymfonyStyle : fix blocks failed when $messages is null.

src/Symfony/Component/Console/Style/SymfonyStyle.php

@@ -60,7 +60,7 @@ class SymfonyStyle extends OutputStyle
      */
     public function block($messages, $type = null, $style = null, $prefix = ' ', $padding = false)
     {
-        $messages = array_values((array) $messages);
+        $messages = is_array($messages) ? array_values($messages) : array($messages);
         $lines = array();
 
         // add type