testing a loopback device without filesystem causes a crash

[ago]

Dear all,

On fezie's request I am reporting a possible bug that I experienced
when running the following:

loopback loop0 /path/to/myfile
if [ -e (loop0)/some/file ]; then
 echo ok
fi

If /path/to/myfile does not contain a filesystem, grub2 crashes (there
is a sudden restart) when I run the test.
The ls command works.

ls (loop0) => Device loop0: Unknown filesystem