Merge pull request #665 from tanelj/escape_filter_nil_fix

Fixed issue where "nil" value for "escape" filter breaks rendering

lib/liquid/standardfilters.rb

@@ -33,7 +33,7 @@ module Liquid
     end
 
     def escape(input)
-      CGI.escapeHTML(input).untaint
+      CGI.escapeHTML(input).untaint unless input.nil?
     end
     alias_method :h, :escape
 

test/integration/standard_filter_test.rb

@@ -118,6 +118,7 @@ class StandardFiltersTest < Minitest::Test
 
   def test_escape
     assert_equal '&lt;strong&gt;', @filters.escape('<strong>')
+    assert_equal nil, @filters.escape(nil)
     assert_equal '&lt;strong&gt;', @filters.h('<strong>')
   end