Fix for [perl #52074] Segfault on ISA push after symbol table delete

This restores the 5.8.8 behaviour. The deleted stash is not vivified
again, hence the hierarchy remains broken. But there's no segfault.

p4raw-id: //depot/perl@33684

1 files changed, 5 insertions, 1 deletions

diff --git a/t/mro/pkg_gen.t b/t/mro/pkg_gen.t
index 6a507ac24d..e1f5eb0e8a 100644
--- a/t/mro/pkg_gen.t
+++ b/t/mro/pkg_gen.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 chdir 't' if -d 't';
-require q(./test.pl); plan(tests => 6);
+require q(./test.pl); plan(tests => 7);
 
 {
     package Foo;
@@ -34,3 +34,7 @@ is(mro::get_pkg_gen('Foo'), 1, "pkg_gen 1 for undef %Pkg::");
 
 delete $::{"Foo::"};
 is(mro::get_pkg_gen('Foo'), 0, 'pkg_gen 0 for delete $::{Pkg::}');
+
+delete $::{"Quux::"};
+push @Quux::ISA, "Woot"; # should not segfault
+ok(1, "No segfault on modification of ISA in a deleted stash");