Handling properties of a class that are assigned using an asynchronous function

Question

In a scenario where I have a class ShopManager with a property _itemCategories whose value is going to be set to the return value of an asynchronous function, since I couldn't use async/await inside the class' constructor, I declared an init async function which would be called from the outside and would set its value.

However, the initial value of _itemCategories, before init is called, would be either null or undefined. This makes me have to check if an instance of ShopManager's itemCategories is present every single time I use it anywhere on my application, which isn't ideal.

import type { Application } from '../application';

export class ShopManager {
    private readonly _application: Application;
    private _itemCategories: string[] | null = null;

    public get itemCategories() {
        return this._itemCategories;
    }
    
    public constructor(application: Application) {
        this._application = application;
    }

    public async init() {
        this._itemCategories = await this._getItemCategories();
    }

    private async _getItemCategories(): Promise<string[]> {
        const categories = await this._application.storage.itemCategory.findMany();
        return categories.map((category) => category.name);
    }
}

I'm wondering if there's a better way to set properties of classes based on the return of asynchronous functions, or if I can somehow make TypeScript infer that itemCategories is present after calling init (extremely unlikely I believe).