Undefined lex sub used as inherited method crashes

Thanks to misuse of CvGV.

$ perl5.19.5 -XMfeature=:all -e 'my sub foo {} undef &foo; *UNIVERSAL::bar = \&foo; main->bar()'
Segmentation fault: 11

When deciding under which name to autoload the sub, we can’t assume
CvGV(that_sub) is a GV, as it may be null.

1 files changed, 1 insertions, 1 deletions

diff --git a/gv.c b/gv.c
index e7ef9a7ec4..2b8812923b 100644
--- a/gv.c
+++ b/gv.c
@@ -1057,7 +1057,7 @@ Perl_gv_fetchmethod_pvn_flags(pTHX_ HV *stash, const char *name, const STRLEN le
 	    GV* stubgv;
 	    GV* autogv;
 
-	    if (CvANON(cv))
+	    if (CvANON(cv) || !CvGV(cv))
 		stubgv = gv;
 	    else {
 		stubgv = CvGV(cv);