System.Xml.Xsl.XslTransformException: An error occurred during a call to extension function 'GetProducts'. See InnerException for a complete description of the error. ---> System.ArgumentNullException: Value cannot be null.
Parameter name: index
   at Sitecore.Diagnostics.Assert.ArgumentNotNull(Object argument, String argumentName)
   at Sitecore.ItemBucket.Kernel.Util.QueryTranslator..ctor(ILuceneIndex index)
   at Sitecore.ItemBucket.Kernel.Util.IndexSearcher.GetItems(DateRangeSearchParam param)
   at Sitecore.ItemBucket.Kernel.ItemExtensions.Axes.ItemExtensions.Search(Item itm, SafeDictionary`1 refinements, Int32& hitCount, String relatedIds, String indexName, String text, String templates, String location, String language, String id, String sortField, String itemName, String startDate, Int32 pageNumber, String endDate, String sortDirection, Int32 numberOfItemsToReturn, Object[] parameters)
   at Illumi.BLL.Ecommerce.Custom.Facets.FieldFacet.Filter(Query query, List`1 searchQuery, String locationFilter, BitArray baseQuery) in D:\github\bll-airport\Illumi.BLL.Custom\Facets\FieldFacet.cs:line 95
   at Illumi.BLL.Ecommerce.Integrations.Search.ProductSearch.GetFacets(Index index, Query query) in D:\github\bll-airport\Illumi.BLL.Ecommerce\Search\ProductSearch.cs:line 170
   at Illumi.BLL.Ecommerce.Integrations.Search.ProductSearch.GetProducts(SearchQuery searchQuery) in D:\github\bll-airport\Illumi.BLL.Ecommerce\Search\ProductSearch.cs:line 90
   at Illumi.BLL.Ecommerce.Integrations.DAO.SC.SitecoreDataContext.FindProducts(Int32 numberOfItemsToReturn, Int32 pageNumber, String sortField, SortDirection sortDirection, String category, String language, Boolean onlyDiscountedProduct, Boolean onlyEuProducts, String productCodeToExclude, String searchString, List`1 facets, Boolean randomize) in D:\github\bll-airport\Illumi.BLL.Ecommerce\DAO\SitecoreDataContext.cs:line 175
   at Illumi.BLL.Ecommerce.Custom.Helpers.FindProducts(Int32 numberOfItemsToReturn, Int32 pageNumber, ProductSortOrder sortyBy, UrlString urlString, Boolean onlyDiscountedProducts, String productCodeToExclude, Boolean onlyEuProducts, String searchString) in D:\github\bll-airport\Illumi.BLL.Custom\Helpers.cs:line 469
   at Illumi.BLL.XsltExtentions.Extentions.GetProducts(Boolean onlyDiscountedProducts, String productCodesToExclude, Int32 numberOfItemsToReturn, Int32 pageNumber, Int32 itemSorting) in D:\github\bll-airport\Illumi.BLL.XsltExtentions\Extentions.cs:line 683
   at Illumi.BLL.XsltExtentions.Extentions.GetProducts(Int32 numberOfItemsToReturn, Int32 pageNumber, Int32 itemSorting) in D:\github\bll-airport\Illumi.BLL.XsltExtentions\Extentions.cs:line 632
   --- End of inner exception stack trace ---
   at System.Xml.Xsl.Runtime.XmlExtensionFunction.Invoke(Object extObj, Object[] args)
   at System.Xml.Xsl.Runtime.XmlQueryContext.InvokeXsltLateBoundFunction(String name, String namespaceUri, IList`1[] args)
   at Products(XmlQueryRuntime {urn:schemas-microsoft-com:xslt-debug}runtime)
   at Execute(XmlQueryRuntime {urn:schemas-microsoft-com:xslt-debug}runtime)
   at System.Xml.Xsl.XmlILCommand.Execute(Object defaultDocument, XmlResolver dataSources, XsltArgumentList argumentList, XmlWriter writer)
   at System.Xml.Xsl.XslCompiledTransform.Transform(IXPathNavigable input, XsltArgumentList arguments, XmlWriter results)
   at Mvp.Xml.Common.Xsl.MvpXslTransform.TransformToWriter(XmlInput defaultDocument, XsltArgumentList xsltArgs, XmlWriter xmlWriter)
   at Mvp.Xml.Common.Xsl.MvpXslTransform.Transform(XmlInput input, XsltArgumentList arguments, XmlOutput output)
   at Sitecore.Web.UI.WebControls.XslFile.DoRender(HtmlTextWriter output, Item item) Xsl file could not be processed: /illumi/xsl/billund_productlist.xslt