Minor fix for Windows 8

Author: Redth

PushSharp.Windows/WindowsPushChannel.cs

@@ -182,7 +182,7 @@ WindowsNotificationStatus ParseStatus(HttpWebResponse resp, WindowsNotification
 			result.HttpStatus = resp.StatusCode;
 
 			var wnsDebugTrace = resp.Headers["X-WNS-Debug-Trace"];
-			var wnsDeviceConnectionStatus = resp.Headers["X-WNS-DeviceConnectionStatus"];
+			var wnsDeviceConnectionStatus = resp.Headers["X-WNS-DeviceConnectionStatus"] ?? "connected";
 			var wnsErrorDescription = resp.Headers["X-WNS-Error-Description"];
 			var wnsMsgId = resp.Headers["X-WNS-Msg-ID"];
 			var wnsNotificationStatus = resp.Headers["X-WNS-NotificationStatus"];