Ensure that all items passed to rendering are element types

src/Umbraco.Core/Models/PublishedContent/PublishedContentType.cs

@@ -31,6 +31,8 @@ namespace Umbraco.Core.Models.PublishedContent
 
             _propertyTypes = propertyTypes.ToArray();
 
+            IsElement = contentType.IsElement;
+
             InitializeIndexes();
         }
 
@@ -166,6 +168,11 @@ namespace Umbraco.Core.Models.PublishedContent
             return index >= 0 && index < _propertyTypes.Length ? _propertyTypes[index] : null;
         }
 
+        /// <summary>
+        /// Gets a value indicating whether this content type is for an element.
+        /// </summary>
+        public bool IsElement { get; }
+
         #endregion
     }
 }

src/Umbraco.Web/PropertyEditors/ValueConverters/NestedContentValueConverterBase.cs

@@ -45,8 +45,9 @@ namespace Umbraco.Web.PropertyEditors.ValueConverters
             if (string.IsNullOrEmpty(elementTypeAlias))
                 return null;
 
+            // only convert element types - content types will cause an exception when PublishedModelFactory creates the model
             var publishedContentType = _publishedSnapshotAccessor.PublishedSnapshot.Content.GetContentType(elementTypeAlias);
-            if (publishedContentType == null)
+            if (publishedContentType == null || publishedContentType.IsElement == false)
                 return null;
 
             var propertyValues = sourceObject.ToObject<Dictionary<string, object>>();