Collection_navigation_equal_to_null_for_subquery fails after merging from release/6.0

[ajcvickers]

All providers.

[ConditionalTheory]
[MemberData(nameof(IsAsyncData))]
public virtual Task Collection_navigation_equal_to_null_for_subquery(bool async)
    => AssertQuery(
        async,
        ss => ss.Set<Customer>().Where(c => c.Orders.OrderBy(o => o.OrderID).FirstOrDefault().OrderDetails == null),
        ss => ss.Set<Customer>().Where(c => c.Orders.OrderBy(o => o.OrderID).FirstOrDefault() == null),
        entryCount: 2);

The LINQ expression 'DbSet<Customer>()
    .Where(c => DbSet<Order>()
        .Where(o => EF.Property<string>(c, "CustomerID") != null && object.Equals(
            objA: EF.Property<string>(c, "CustomerID"), 
            objB: EF.Property<string>(o, "CustomerID")))
        .OrderBy(o => o.OrderID)
        .Select(o => MaterializeCollectionNavigation(
            Navigation: Order.OrderDetails,
            subquery: DbSet<OrderDetail>()
                .Where(o0 => EF.Property<int?>(o, "OrderID") != null && object.Equals(
                    objA: (object)EF.Property<int?>(o, "OrderID"), 
                    objB: (object)EF.Property<int?>(o0, "OrderID")))))
        .FirstOrDefault() == null)' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.