Hi,

I'm having some trouble with the product content type feature. I've created a new Product Content Type based on a document type with no template, and once I associate it with a product, the entire product listing (All Products) crashes when fetching products from /umbraco/backoffice/Merchello/ProductApi/SearchProducts. I get the following exception:

{
    "exceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.",
    "exceptionType": "System.InvalidOperationException",
    "innerException": {
        "exceptionMessage": "Object reference not set to an instance of an object.",
        "exceptionType": "System.NullReferenceException",
        "message": "An error has occurred.",
        "stackTrace": "
            at Merchello.Web.Models.ContentEditing.ExamineDisplayExtensions.GetProductVariantDetachedContentDisplayCollection(SearchResult result, String alias)\r\n
            at Merchello.Web.Models.ContentEditing.ExamineDisplayExtensions.ToProductVariantDisplay(SearchResult result)\r\n
            at Merchello.Web.Search.CachedProductQuery.PerformMapSearchResultToDisplayObject(SearchResult result)\r\n
            at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()\r\n
            at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)\r\n
            at Merchello.Web.Search.CachedProductQuery.GetDisplayObject(Guid key)\r\n
            at Merchello.Web.Search.QueryResultFactory`1.<BuildQueryResult>b__2(Guid x)\r\n
            at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext()\r\n
            at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n
            at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n
            at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n
            at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n
            at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n
            at System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n
            at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n
            --- End of stack trace from previous location where exception was thrown ---\r\n
            at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n
            at System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()"
    },
    "message": "An error has occurred.",
    "stackTrace": null
}

However, everything starts working again if I remove the product content type. Does anyone have a clue of what could be causing this? I'm running Umbraco 7.3.5 and Merchello 1.14.1.