Filesystem.System()->find() is broken.

The filtering of in find() attempts to call the value 1 (if there are any subdirectories). This seems to be code that was missed in 9ae59318:

array find(void|function(Filesystem.Stat, __unknown__...:int) mask,
	   mixed ... extra)
{
  array(Filesystem.Stat) res = ({});
  array(Filesystem.Stat) d = get_stats() || ({});
  array(Filesystem.Stat) r = filter(d, "isdir");