crnlib: don't stop listing files if there is an unknown file type in a directory, skip it

[illwieckz]

Don't stop listing files if there is an unknown file type in a directory, skip it.

[illwieckz]

We may have a more generic thinking about what we want there, for example, we may still want to accept some character file so we can convert files by piping them through /dev/stdin or so, or have a more generic thinking about globbing and the waste of listing every parent folder of every file.

But this patch is enough to fix the related bug, where a file cannot be converted because there is a fifo in the same folder.