Issues Migrating commerce

I am new to commerce and i am running into an issue during the migration set. 

    12:06:10 PM: Completed migration step: Migrates published Catalog Content
    12:06:10 PM: Migrates published Catalog Content has failed with exception 'System.ArgumentNullException: Value cannot be null. Parameter name: key at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at EPiServer.Commerce.Internal.Migration.Steps.MigratePublishedContentStep.ListPropertyData(MetaClass metaClass, String language, Int32 objectTypeId, Int32 count, DataTable propertyData, DataTable contentExData, DataTable idsToDelete) at EPiServer.Commerce.Internal.Migration.Steps.MigratePublishedContentStep.MigrateCatalogContent(MetaClass metaClass, IList`1 languages) at EPiServer.Commerce.Internal.Migration.Steps.MigratePublishedContentStep.Execute(IProgressMessenger progressMessenger)'.
    12:06:10 PM: Migrating table 'CatalogNodeEx'.
    12:06:10 PM: Migrating Catalog.
    12:06:10 PM: Starting migration step: Migrates published Catalog Content

Appears to happen on this step: Migrates published Catalog Content

Is there something i am missing?  Any advice would be great.