Response status code default is 200

fixes #1220

framework/yii/web/Response.php

@@ -126,9 +126,10 @@ class Response extends \yii\base\Response
 	 */
 	public $charset;
 	/**
-	 * @var string
+	 * @var string the HTTP status description that comes together with the status code.
+	 * @see [[httpStatuses]]
 	 */
-	public $statusText;
+	public $statusText = 'OK';
 	/**
 	 * @var string the version of the HTTP protocol to use. If not set, it will be determined via `$_SERVER['SERVER_PROTOCOL']`,
 	 * or '1.1' if that is not available.
@@ -208,7 +209,7 @@ class Response extends \yii\base\Response
 	/**
 	 * @var integer the HTTP status code to send with the response.
 	 */
-	private $_statusCode;
+	private $_statusCode = 200;
 	/**
 	 * @var HeaderCollection
 	 */
@@ -248,11 +249,6 @@ class Response extends \yii\base\Response
 	 */
 	public function setStatusCode($value, $text = null)
 	{
-		if ($value === null) {
-			$this->_statusCode = null;
-			$this->statusText = null;
-			return;
-		}
 		$this->_statusCode = (int)$value;
 		if ($this->getIsInvalid()) {
 			throw new InvalidParamException("The HTTP status code is invalid: $value");
@@ -297,10 +293,10 @@ class Response extends \yii\base\Response
 	{
 		$this->_headers = null;
 		$this->_cookies = null;
-		$this->_statusCode = null;
+		$this->_statusCode = 200;
+		$this->statusText = 'OK';
 		$this->data = null;
 		$this->content = null;
-		$this->statusText = null;
 	}
 
 	/**
@@ -312,9 +308,7 @@ class Response extends \yii\base\Response
 			return;
 		}
 		$statusCode = $this->getStatusCode();
-		if ($statusCode !== null) {
 		header("HTTP/{$this->version} $statusCode {$this->statusText}");
-		}
 		if ($this->_headers) {
 			$headers = $this->getHeaders();
 			foreach ($headers as $name => $values) {