Files with unknown MIME type do not display emblem icons

Affected version

• Nightly flatpak: Yes
• Other: Arch Linux (version 3.32.1-1); Ubuntu 18.04 (version 1:3.26.4-0)

Steps to reproduce

1. Install an extension that provides emblems (I tested using a small test project and nautilus-dropbox.
2. Create a file full of NUL characters with no extension (e.g. dd bs=4M count=10 if=/dev/zero of=/home/colin/Dropbox/noext). The fact that it's NUL is actually significant--this guarantees that the MIME type will not be determinable.
3. Find the file in nautilus.

Current behavior

Unlike other files, the newly-created one will not have an emblem.

Expected behavior

Ideally, it would have an emblem.

Additional information

The issue seems to be in nautilus_file_get_icon in the branch that is activated when nautilus_icon_info_is_fallback (icon ) returns true. I have a patch that I will submit shortly, but I figured I would create a proper ticket for discussion/documentation.