`Cannot read properties of undefined (reading 'id')` when the app is not installed

[ari-becker]

Environment

N/A

Steps to Reproduce

1. Create an app, produce a private key
2. Forget to install it
3. Run a workflow that uses this step

Expected Result

An error message stating that no installations were found.

Actual Result

The error occurs because

action-github-app-token/src/main.ts

Line 25 in 86b9938

let installationId = installations.data[0].id;

presumes that there is at least one installation in the returned array.