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, 2 insertions, 4 deletions

diff --git a/mro.c b/mro.c
index 7074e7ab72..37573f1eec 100644
--- a/mro.c
+++ b/mro.c
@@ -455,10 +455,8 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
     bool is_universal;
     struct mro_meta * meta;
 
-    const char * const stashname = stash ? HvNAME_get(stash) : NULL;
-    const STRLEN stashname_len = stash ? HvNAMELEN_get(stash) : 0;
-
-    if(!stash) return;
+    const char * const stashname = HvNAME_get(stash);
+    const STRLEN stashname_len = HvNAMELEN_get(stash);
 
     if(!stashname)
         Perl_croak(aTHX_ "Can't call mro_isa_changed_in() on anonymous symbol table");