I realize that there is a new version (4.7) of Umbraco coming out, but I need to publish a macro for a running site tonight.  This is the first time that I have used Razor, so I'm sure I'm doing something wrong, but I have the following error message:

An unknown error occured while rendering the following code:
System.NullReferenceException: Object reference not set to an instance of an object. at RazorEngine.Dynamic.baeffbebc.Execute() at RazorEngine.Templating.TemplateService.Parse[T](String template, T model, String name) at umbraco.MacroEngines.RazorEngine.GetResult(String cacheIdentifier, String template, INode currentPage, String& result)

My macro looks like this:

@using System
@using uComponents.Core
@using uComponents.Core.uQueryExtensions
@using System.Linq
@using umbraco.NodeFactory
@helper NoPictures()
{
 <li>Pictures coming soon!</li>
}

@helper Pictures(String crop)
{
 <li><a rel="photos" href="@crop" title="test">
        <img src="@crop" class="shadow hovershadow"></a></li>
}
@{
   var n = Node.GetCurrent();
   var pictures = n.GetProperty("pictures").Value;
   if(pictures.Length <= 0)
   {
     NoPictures();
   }
   else
   {
     var pictureNodes = pictures.Split(',');
     
     foreach (var pictureNode in pictureNodes)
     {
      var node = new Node(Convert.ToInt32(pictureNode));
      var photoId = node.GetProperty("picture").Value;
      var photo = uComponents.Core.uQuery.GetMedia(Convert.ToInt32(photoId));
      var crop = MediaExtensions.GetImageCropperUrl(photo, "umbracoFile", "wide");
      Pictures(crop);
     }
   }
}

Thank you so much for the help.