Argument of type Inventory is not assignable to parameter of type never

Question

Creating an Ionic app from some tutorial and can not figure out what is wrong here. I got 2 messages about the code:

let a = item.payload.toJSON();
        a['$key'] = item.key;
        this.Bookings.push(a as Inventory);

The messages are:

*- 'a' is possibly 'null'.

• Argument of type 'Inventory' is not assignable to parameter of type 'never'.*

I tried to disable messages in the tsconfig.json file, messages are gone but it still is not working so somehow i have to solve this.