You use :
.item_list[.@i] = rand( 901,968 );
Which means randomly choose an item from item id 901 -> 968. Unfortunately we don't have item 927 and 933 and that will result to null values
926,Scale_Of_Snakes,Snake Scale,3,82,,10,,,,,,,,,,,,,{},{},{}
928,Insect_Feeler,Insect Feeler,3,114,,10,,,,,,,,,,,,,{},{},{}
929,Immortal_Heart,Immortal Heart,3,374,,10,,,,,,,,,,,,,{},{},{}
930,Rotten_Bandage,Rotten Bandage,3,350,,10,,,,,,,,,,,,,{},{},{}
931,Orcish_Voucher,Orcish Voucher,3,142,,10,,,,,,,,,,,,,{},{},{}
932,Skel_Bone,Skel-Bone,3,232,,10,,,,,,,,,,,,,{},{},{}
934,Mementos,Memento,3,600,,10,,,,,,,,,,,,,{},{},{}
Reference : db/pre-re/item_db.txt | db/re/item_db.txt