Hi,

this patch fixes lto PR70187, a 6 regression.

We run into an ICE in in possible_polymorphic_call_targets when 
accessing nodes[0]->decl because nodes == vNULL:
...
   if (!outer_type->all_derivations_known)
     {
       if (!speculative && final_warning_records
           && TREE_CODE (TREE_TYPE (nodes[0]->decl)) == METHOD_TYPE)
         {
           if (complete
               && nodes.length () == 1
               && warn_suggest_final_types
               && !outer_type->derived_types.length ())
             {
...

The patch fixes this by moving the 'nodes.length () == 1' test to before 
the use of nodes[0].

Bootstrapped and reg-tested on x86_64.

OK for stage4 trunk?

Thanks,
- Tom