Upload manager: empty integer fields not allowed

I'm using the Upload Manager to get my CSV-data into Firebase. I've got a table with integer and string fields, exclusively. Now, the validation step before uploading does NOT accept empty integer fields (which, e.g., may only be populated later), whereas empty fields work just fine for string type fields.

For the time being, I've subsituted 0 for the empty integer fields; but surely, empty should be an option even for integer type fields??

Thanks for any ideas or insights on this.

-- The Upload Manager error (see screenshot) is white type on gray bg, which makes it hard to read... but that's another issue 😉 .