Disabling submit button until file has loaded through presign endpoint

I’m using Uppy with Shrine in a Rails app, and one thing I notice immediately after implementing direct s3 uploads is that the submit button can be clicked before the GET request is completed. If this happens, the action fails as no file is attached for Shrine to work with.

How would I go about disabling my submit button until that GET request is complete? Thank you for your help!