Revert change #31489.

That change was adding a hook to cope with the case when one was
undef'ining *ISA globs, in order to clean up correctly. However, this
broke the case where one was assiging an array ref to @ISA, which
is likely to be more common.
Conclusion: don't undef *ISA. (or more generally don't undef globs
that contain magical variables)
p4raw-link: @31489 on //depot/perl: 5be5c7a687aa37f2ea9dec7988eb57cad1f1ec24

p4raw-id: //depot/perl@31502

1 files changed, 1 insertions, 1 deletions

diff --git a/perl.h b/perl.h
index d59ac351c5..3877de1070 100644
--- a/perl.h
+++ b/perl.h
@@ -4768,7 +4768,7 @@ MGVTBL_SET(
     MEMBER_TO_FPTR(Perl_magic_setisa),
     0,
     MEMBER_TO_FPTR(Perl_magic_setisa),
-    MEMBER_TO_FPTR(Perl_magic_freeisa),
+    0,
     0,
     0,
     0