lower_dw must deactivate edges

There might be some ProjL nodes reachable via out edges
and the following "local" phase does enqueue_users for
optimized nodes, which might visit the 'undead' ProjL.

ir/lower/lower_dw.c

@@ -2574,6 +2574,7 @@ static void lower_irg(ir_graph *irg)
 			set_irg_doms_inconsistent(irg);
 			set_irg_extblk_inconsistent(irg);
 		}
+		edges_deactivate(irg);
 	}
 
 	ir_free_resources(irg, IR_RESOURCE_PHI_LIST | IR_RESOURCE_IRN_LINK);