filesystem: fixed script 'dune' crash on update

Crashing occurred when there was no etc/*-saved.ini file.
Happens at least for every system that is running for the first time.

packages/filesystem/fs/etc/rc.d/dune

@@ -14,7 +14,9 @@ maybe_upgrade()
     rm -rf $dune_base/.dune-upgrade &&
     mkdir $dune_base/.dune-upgrade &&
     tar -x -C $dune_base/.dune-upgrade -f $dune_base/dune-*.tar.bz2 &&
-    cp "$dune_base/etc/"*-saved.ini "$dune_base/.dune-upgrade/"dune-*/etc 2> /dev/null &&
+    if [ -f $dune_base/etc/*-saved.ini ]; then
+        cp "$dune_base/etc/"*-saved.ini "$dune_base/.dune-upgrade/"dune-*/etc 2> /dev/null
+    fi &&
     rm $dune_base/dune-*.tar.bz2 &&
     for dir in $dune_base/.dune-upgrade/dune-*/*; do
         d="$(basename "$dir")"