[perl #128238] Crash with non-stash in stash

This is a follow-up to e7acdfe.  Even if the name of the stash
entry ends with ::, it may not itself contain a real stash (though
this only happens with code that assigns directly to stash entries,
which has undefined behaviour according to perlmod), so skip hashes
that are not stashes.

Author: Father Chrysostomos

.git-rr-cache

@@ -2438,10 +2438,10 @@ Perl_gv_check(pTHX_ HV *stash)
 
     PERL_ARGS_ASSERT_GV_CHECK;
 
-    if (!HvARRAY(stash))
+    if (!SvOOK(stash))
 	return;
 
-    assert(SvOOK(stash));
+    assert(HvARRAY(stash));
 
     for (i = 0; i <= (I32) HvMAX(stash); i++) {
         const HE *entry;