Can't select file on file browser after changing sort order

The row values are 1-indexed not 0-indexed, this has to be taken into
account when producing the new_order array.

https://bugzilla.gnome.org/show_bug.cgi?id=621414

gtk/gtkfilesystemmodel.c

@@ -739,7 +739,7 @@ gtk_file_system_model_sort (GtkFileSystemModel *model)
                   continue;
                 }
 
-              new_order[r] = node->row;
+              new_order[r] = node->row - 1;
               r++;
               node->row = r;
             }