remove wrong debug assert in block readers (#6604)

Author: fedor-miron

ydb/library/yql/public/udf/arrow/block_reader.h

@@ -40,8 +40,6 @@ class TFixedSizeBlockReaderBase : public IBlockReader {
             if (IsNull(data, index)) {
                 return {};
             }
-        } else {
-            Y_DEBUG_ABORT_UNLESS(!data.MayHaveNulls());
         }
         return static_cast<TDerived*>(this)->MakeBlockItem(data.GetValues<T>(1)[index]);
     }
@@ -131,8 +129,6 @@ class TStringBlockReader final : public IBlockReader {
             if (IsNull(data, index)) {
                 return {};
             }
-        } else {
-            Y_DEBUG_ABORT_UNLESS(!data.MayHaveNulls());
         }
 
         const TOffset* offsets = data.GetValues<TOffset>(1);
@@ -214,8 +210,6 @@ class TTupleBlockReaderBase : public IBlockReader {
         if constexpr (Nullable) {
             if (IsNull(data, index)) {
                 return {};
-            } else {
-                Y_DEBUG_ABORT_UNLESS(!data.MayHaveNulls());
             }
         }
         return static_cast<TDerived*>(this)->GetChildrenItems(data, index);