NullReferenceException on call to Ignore()

[divega]

Note that I haven't tried to repro this with the latest bits buts I am copying from comment #3727 (comment) by @miroslavsiska and is the same repro as #3863 but with the call to Ignore<AllergenQuantity>() added. In the end this is an invalid model.

According to the comment the Ignore() call fails with NullReferneceException:

public class AllergenQuantity
{              
    public Guid UnitId { get; set; }
    public virtual Unit Unit { get; set; }         

    [Display(Name = "Množství obsahu")]
    public decimal Quantity { get; set; }
}


 public class Unit 
{
    public Unit()
    {
        this.Id = Guid.NewGuid();
    }
    public virtual ICollection<AllergenQuantity> AllergenQuantity { get; set; }

    [Key]
    public Guid Id { get; set; }     

    [Display(Name = "Jednotka")]
    public string Name { get; set; }

    [Display(Name = "Typ Jednotky")]
    public string UnitType { get; set; }

    [Display(Name = "Použité v kulturách")]
    public string Cultures { get; set; }
}


  public class TenantDbContext : IdentityDbContext<TenantUser, TenantRole, Guid>
{
    private string _connectionString { get; set; }

    public TenantDbContext(DbContextOptions<TenantDbContext> options) : base(options) 
    {
        this._connectionString = "CON STRING";
    }

    public TenantDbContext()       
    {
    }   
    public TenantDbContext(string ConnectionString)
    {
        this._connectionString = ConnectionString;
    }
    public static TenantDbContext Create(string ConnectionString)
    {
        return new TenantDbContext(ConnectionString);
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    { 
        optionsBuilder.UseSqlServer(_connectionString);  
    }

    //  BASE
    public DbSet<Unit> Unit { get; set; }

    //  Stock
    public DbSet<Allergen> Allergen { get; set; }  
    public DbSet<AllergenQuantityMaterial> AllergenQuantityMaterial { get; set; }        //Inherited from AllergenQuantity
    public DbSet<Material> Material { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {      
        base.OnModelCreating(builder);
        // throws reference not set to object instance...
        builder.Ignore<AllergenQuantity>();   
        //Composites keys mapping
        builder.Entity<AllergenQuantityMaterial>().HasKey(l => new { l.MaterialId, l.AllergenId });  
    }
}

.

[smitpatel]

This is working in latest code now.
Possible reason for the exception
https://github.com/aspnet/EntityFramework/blob/7.0.0-rc1/src/EntityFramework.Core/Metadata/Internal/InternalEntityTypeBuilder.cs#L302
The base entity type builder returning null. Since the implementation in metadata changed in this area after rc1 it does not repro anymore.