PR32858 ld segfault on fuzzed object

[Alan Modra]

We missed one place where it is necessary to check for empty groups.

	PR 32858
	* elflink.c (elf_gc_sweep): Protect against empty group.

diff --git a/bfd/elflink.c b/bfd/elflink.c
index a76e8e38da7..549b7b7dd92 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -14408,7 +14408,8 @@ elf_gc_sweep (bfd *abfd, struct bfd_link_info *info)
 	  if (o->flags & SEC_GROUP)
 	    {
 	      asection *first = elf_next_in_group (o);
-	      o->gc_mark = first->gc_mark;
+	      if (first != NULL)
+		o->gc_mark = first->gc_mark;
 	    }
 
 	  if (o->gc_mark)

-- 
Alan Modra