Check that stash entries are GVs when aliasing pkgs

$ perl5.18.1 -e '$Foo::{"Bar::"} = 0; $Bar::Bar::; *Bar:: = *Foo::'
Segmentation fault: 11

That $Foo::{"Bar::"} = 0; assignment is documented as having unde-
fined behaviour, but it shouldn’t crash.

1 files changed, 1 insertions, 1 deletions

diff --git a/mro.c b/mro.c
index 18dfa8c011..04b3c273dc 100644
--- a/mro.c
+++ b/mro.c
@@ -1151,7 +1151,7 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
 
 		    if(
 		        (
-		            stashentry && *stashentry
+		            stashentry && *stashentry && isGV(*stashentry)
 		         && (substash = GvHV(*stashentry))
 		        )
 		     || (oldsubstash && HvENAME_get(oldsubstash))