Typescript typing problem when trying to declare a column "not null"

[shorn]

I currently have table public_user_info with a nullable display_name column; I recently decided to make display_name non-nullable.

The SQL to alter the table:

alter table public.public_user_info
  alter column display_name set default '',
  alter column display_name set not null;

So I want to update my client-side public_user_info2 interface structure to reflect that column is now mandatory.

But when I do that, the Typescript compiler gives me the error:

TypeScript error in C:/projects/cabbage/app/src/Api/CabbageApi.ts(26,18):
Argument of type 'string | undefined' is not assignable to parameter of type 'string'.
  Type 'undefined' is not assignable to type 'string'.  TS2345

    24 |     await db.from<public_user_info2>('public_user_info').
    25 |       select('display_name').
  > 26 |       eq("uuid", db.auth.user()?.id);
       |                  ^
    27 |
    28 |   return queryResult;
    29 | }

The code looks like this:

import SupabaseClient from "@supabase/supabase-js/dist/main/SupabaseClient";
import {PostgrestResponse} from "@supabase/postgrest-js/dist/main/lib/types";

interface public_user_info2 {
  uuid: string,
  display_name?: string 
}

export async function queryDisplayNameOnly(db: SupabaseClient){
  const queryResult: PostgrestResponse<public_user_info2> =
    await db.from<public_user_info2>('public_user_info').
      select('display_name').
      eq("uuid", db.auth.user()?.id);

  return queryResult;
}

The error is caused when I try to change display_name?: string to be declared display_name: string.

What am I doing wrong?

The code for this project ( so package.json, etc.) is available on Github.
I am using "@supabase/supabase-js": "1.3.4"