can't assign class with attributes to undef

[coke]

See TT #696 for the original version of this.

Modified version that causes segfault against r39187.

.sub main :main
  say "1..2"

  $P0 = new "Undef"
  $P2 = new 'Integer'
  assign $P0, $P2
  say "ok 1"

  $P0 = new "Undef"
  $P1 = get_class 'Hash'
  $P2 = subclass $P1
  addattribute $P2, 'searches'
  addattribute $P2, 'ids'

  $P3 = new $P2
  assign $P0, $P3
  say "ok 2"
.end

generates

1..2
ok 1
get_attr_str() not implemented in class 'default'
current instr.: 'main' pc 31 (foo.pir:16)
destroy() not implemented in class 'default'
current instr.: 'main' pc 31 (foo.pir:16)
Segmentation fault

[coke]

This is no longer a blocker for partcl.

[coke]

Replying to coke:

This is no longer a blocker for partcl.

[bacek]

Example from original description at r41527 produces

1..2
ok 1
ok 2

Resolving ticket.