Add missing trivial clauses to record rewriter

Author: alco

lib/elixir/lib/kernel/record_rewriter.ex

@@ -350,6 +350,10 @@ defmodule Kernel.RecordRewriter do
     vars
   end
 
+  defp join_dict([]) do
+    []
+  end
+
   defp join_dict([{ _, dict, _ }|t]) do
     join_dict(t, dict)
   end
@@ -374,6 +378,10 @@ defmodule Kernel.RecordRewriter do
     other
   end
 
+  defp join_result([]) do
+    []
+  end
+
   defp join_result([{ _, _, res }|t]) do
     join_result(t, res)
   end