fix rendering of multiple dropdowns question in rails 3

refs CNVS-13790

test plan:
 * create a quiz with a multiple drop downs question
 * preview it
 * it should render correctly

Change-Id: I8a37e0e7b8eee545252343927f8697b659726de0
Reviewed-on: https://gerrit.instructure.com/37193
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ahmad Amireh <ahmad@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>

app/helpers/quizzes_helper.rb

@@ -441,7 +441,7 @@ module QuizzesHelper
     answer_list = hash_get(options, :answer_list)
     res      = user_content hash_get(question, :question_text)
     index  = 0
-    res.gsub %r{<select.*?name=['"](question_.*?)['"].*?>.*?</select>} do |match|
+    res.to_str.gsub %r{<select.*?name=['"](question_.*?)['"].*?>.*?</select>} do |match|
       if answer_list && !answer_list.empty?
         a = answer_list[index]
         index += 1
@@ -449,7 +449,7 @@ module QuizzesHelper
         a = hash_get(answers, $1)
       end
       match.sub(%r{(<option.*?value=['"]#{ERB::Util.h(a)}['"])}, '\\1 selected')
-    end
+    end.html_safe
   end
 
   def duration_in_minutes(duration_seconds)

spec/helpers/quizzes_helper_spec.rb

@@ -247,6 +247,19 @@ describe QuizzesHelper do
     end
   end
 
+  context "multiple_dropdowns_question" do
+    before do
+      def user_content(stuff); stuff; end # mock #user_content
+    end
+
+    it "should select the user's answer" do
+      html = multiple_dropdowns_question(question: { question_text: "some <select name='question_4'><option value='val'>val</option></select>"},
+                                         answer_list: ['val'])
+      html.should == "some <select name='question_4'><option value='val' selected>val</option></select>"
+      html.should be_html_safe
+    end
+  end
+
   describe "#quiz_edit_text" do
 
     it "returns correct string for survey" do