Fix ipa-icf.c segfault

[Jan Hubicka]

Hi,
this patch fixes segfault that crept into my prevoius patch.

Bootstrapped/regtested x86_64-linux, comitted.

Honza

        * ipa-icf.c (sem_function::merge): Check that local_original exists.
Index: ipa-icf.c
===================================================================
--- ipa-icf.c   (revision 231319)
+++ ipa-icf.c   (working copy)
@@ -1359,7 +1359,9 @@ sem_function::merge (sem_item *alias_ite
     {
       if (dump_file)
        fprintf (dump_file, "Dropping merged_comdat flag.\n\n");
-      local_original->merged_comdat = original->merged_comdat = false;
+      if (local_original)
+        local_original->merged_comdat = false;
+      original->merged_comdat = false;
     }
 
   if (remove)