The cast to value type 'system.boolean' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.

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LINQ

public static void GetByid(long id)
      {
          using (var db = new ClientDbContext(DALContext.LoyaltyGenieWebDbConnectionString))
          {
              List<PromotionCategories> promotioncategories=new List<PromotionCategories>();
              //List<PromotionCategories> promotioncategories = db.PromotionCategories.Where(t => t.PromotionsId == id).ToList();
              var p = (from s in db.PromotionCategories
                       join x in db.QualifyOption on s.Id equals x.PromotionCategoryId
                       into t from cat in t.DefaultIfEmpty()
                       where s.PromotionsId == id
                       select new
                       {
                           s.Id,
                           s.PromotionsId,
                           s.NumberofProducts,
                           s.ActiveStatus,
                           s.CreatedDate,
                           s.ModifiedDate,
                           s.CreatedBy,
                           s.ModifiedBy,
                           s.PromotionCategory,
                           s.CategoryId,
                           s.ProductId,
                           cat.IsOption,
                           cat.OptionId,
                           cat.PromotionCategoryId


                       }).ToList();


          }
      }

.

Please help me.
thank you.

What I have tried:

The cast to value type 'System.Boolean' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.