seg fault in connect_unix()

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=3139

Reported by Robert J. Budzynski, Warsaw University, Dept. of Physics Robert.Budzynski@fuw.edu.pl

test script:
#!/usr/local/bin/pike7.3

int main()
{ // neither of the files "foo" nor "bar" exists
  Stdio.File f = Stdio.File();
  werror("trying connect_unix(\"foo\")...\n");
  f->connect_unix("foo") || Stdio.perror("foo");
  werror("trying connect_unix(\"bar\")...\n");
  f->connect_unix("bar") || Stdio.perror("bar");
  return 0;
}

output:

$ ./socket_unix.pike trying connect_unix("foo")... foo: No such file or directory trying connect_unix("bar")... Segmentation fault