Gmail can’t attach file. “Document contains no data” error

Hi,
I have been using my Gmail account for a very long time and this is the first time that I’m having problems with attaching a file. It is giving me a “Document contains no data” error.

Which is impossible, since the document that I was trying to attach was certainly not blank nor empty. Does anyone know how to go about this issue?
I need to send this email right away.
