Fixes ArgvInput's argument getter with empty tokens

If an empty token is provided (from automated tools, or on purpose when
running a command), the argument getter was not checking the other
tokens, as '' == false in php, which is the stop condition of the while
loop in this method.

This method should now rely on the count of tokens rather than the value
of the return of array_shift

src/Symfony/Component/Console/Input/ArgvInput.php

@@ -309,9 +309,11 @@ class ArgvInput extends Input
     public function getParameterOption($values, $default = false)
     {
         $values = (array) $values;
-
         $tokens = $this->tokens;
-        while ($token = array_shift($tokens)) {
+
+        while (0 < count($tokens)) {
+            $token = array_shift($tokens);
+
             foreach ($values as $value) {
                 if ($token === $value || 0 === strpos($token, $value.'=')) {
                     if (false !== $pos = strpos($token, '=')) {

src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php

@@ -304,6 +304,7 @@ class ArgvInputTest extends \PHPUnit_Framework_TestCase
             array(array('app/console', 'foo:bar', '-e', 'dev'), array('-e', '--env'), 'dev'),
             array(array('app/console', 'foo:bar', '--env=dev'), array('-e', '--env'), 'dev'),
             array(array('app/console', 'foo:bar', '--env=dev', '--en=1'), array('--en'), '1'),
+            array(array('app/console', 'foo:bar', '--env=dev', '', '--en=1'), array('--en'), '1'),
         );
     }