Make parse function be able to handle nil and convert it to empty string

lib/liquid/template.ex

@@ -37,9 +37,15 @@ defmodule Liquid.Template do
   @doc """
   Function to parse markup with given presets (if any)
   """
-  @spec render(String.t, map) :: Liquid.Template
-  def parse(<<markup::binary>>, presets \\ %{}) do
+  @spec parse(String.t, map) :: Liquid.Template
+  def parse(value, presets \\ %{})
+  def parse(<<markup::binary>>, presets) do
     Liquid.Parse.parse(markup, %Template{presets: presets})
   end
 
+  @spec parse(nil, map) :: Liquid.Template
+  def parse(nil, presets) do
+    Liquid.Parse.parse("", %Template{presets: presets})
+  end
+
 end

mix.exs

@@ -3,7 +3,7 @@ defmodule Liquid.Mixfile do
 
   def project do
     [ app: :liquid,
-      version: "0.6.0",
+      version: "0.6.1",
       elixir: "~> 1.3",
       deps: deps(),
       name: "Liquid",

test/liquid/template_test.exs

@@ -30,6 +30,11 @@ defmodule Liquid.TemplateTest do
     assert ["  ", "{% comment %}", " ", "{% endcomment %}", " "] == Parse.tokenize("  {% comment %} {% endcomment %} ")
   end
 
+  test :should_be_able_to_handle_nil_in_parse do
+    t = Template.parse(nil)
+    assert { :ok, "", _context} = Template.render(t)
+  end
+
   test :returns_assigns_from_assign_tags do
     t = Template.parse("{% assign foo = 'from returned assigns' %}{{ foo }}")
     { :ok, rendered, context } = Template.render(t)