ftp: Handle cases where symlink target is not defined
ftp: Handle cases where symlink target is not defined

This can happen when systems emulate ls -l output but fail.
Surprisingly, ProFtpd seems to be one of these.

https://bugzilla.gnome.org/show_bug.cgi?id=608621

philipl/gvfs,halfline/gvfs,philipl/gvfs,xkahn/gvfs-cmis,gicmo/gvfs,xkahn/gvfs-cmis,philipl/gvfs,xkahn/gvfs-cmis,gicmo/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs,cpatulea/gvfs,cpatulea/gvfs,halfline/gvfs,gicmo/gvfs