Added processing of `nil` to `highlight` helper method

actionview/lib/action_view/helpers/text_helper.rb

@@ -126,7 +126,7 @@ def highlight(text, phrases, options = {})
         text = sanitize(text) if options.fetch(:sanitize, true)
 
         if text.blank? || phrases.blank?
-          text
+          text || ""
         else
           match = Array(phrases).map do |p|
             Regexp === p ? p.to_s : Regexp.escape(p)

actionview/test/template/text_helper_test.rb

@@ -193,6 +193,10 @@ def test_highlight_pending
     assert_equal '   ', highlight('   ', 'blank text is returned verbatim')
   end
 
+  def test_highlight_should_return_blank_string_for_nil
+    assert_equal '', highlight(nil, 'blank string is returned for nil')
+  end
+
   def test_highlight_should_sanitize_input
     assert_equal(
       "This is a <mark>beautiful</mark> morning",