Fix preview odata feed

preview.nuget.org feed won't show in VS any more due to breaks I made in Search implementation. This fixes that.

System.InvalidOperationException occurred
  HResult=-2146233079
  Message=The serialized resource has a null value in key member 'Version'. Null values are not supported in key members.
  Source=System.Data.Services
  StackTrace:
       at System.Data.Services.Serializers.Serializer.GetObjectKey(Object resource, DataServiceProviderWrapper provider, String containerName)
  InnerException: 


>	System.Data.Services.dll!System.Data.Services.Serializers.Serializer.GetObjectKey(object resource, System.Data.Services.Providers.DataServiceProviderWrapper provider, string containerName) + 0x16a bytes	
	System.Data.Services.dll!System.Data.Services.Serializers.SyndicationSerializer.WriteEntryElement(System.Data.Services.IExpandedResult expanded, object element, System.Data.Services.Providers.ResourceType expectedType, System.Uri absoluteUri, string relativeUri, System.ServiceModel.Syndication.SyndicationItem target) + 0x149 bytes	
	System.Data.Services.dll!System.Data.Services.Serializers.SyndicationSerializer.DeferredFeedItems.MoveNext() + 0x11f bytes