### What?
Adds validation to the file upload field to ensure a filename is
provided. If the filename is missing, a clear error message is shown to
the user instead of a general error.
### Why?
Currently, attempting to upload a file without a filename results in a
generic error message: `Something went wrong.` This makes it unclear for
users to understand what the issue is.
### How?
The upload field validation has been updated to explicitly check for a
missing filename. If the filename is undefined or null, the error
message `A filename is required` is now shown.
Fixes#13410
5a99d8c5f4