Cookie/ParseTest: fix an incorrect condition

As the `$expected_attributes` and `$expected_flags` variables are optional parameters, these will always be set. However, they may not be set to an array, which is what this condition should protect against.

tests/Cookie/ParseTest.php

@@ -629,13 +629,13 @@ private function check_parsed_cookie($cookie, $expected, $expected_attributes =
  $this->assertSame($expected['expired'], $cookie->is_expired(), 'Cookie expiration identification does not match expectation');
  }
 
- if (isset($expected_attributes) && !empty($expected_attributes)) {
+ if (is_array($expected_attributes) && !empty($expected_attributes)) {
  foreach ($expected_attributes as $attr_key => $attr_val) {
  $this->assertSame($attr_val, $cookie->attributes[$attr_key], "Attribute '$attr_key' should match supplied value");
  }
  }
 
- if (isset($expected_flags) && !empty($expected_flags)) {
+ if (is_array($expected_flags) && !empty($expected_flags)) {
  foreach ($expected_flags as $flag_key => $flag_val) {
  $this->assertSame($flag_val, $cookie->flags[$flag_key], "Flag '$flag_key' should match supplied value");
  }