Bug fix nil parameter ApplicationHelper.markdown

Added specs for nil value parameter and header markdown

app/helpers/application_helper.rb

@@ -254,6 +254,8 @@ module ApplicationHelper
   end
 
   def markdown(text)
+    return '' if text.nil?
+
     options = {
       autolink: true,
       space_after_headers: true,

spec/helpers/application_helper_spec.rb

@@ -22,6 +22,22 @@ describe ApplicationHelper, type: :helper do
     end
   end
 
+  describe 'markdown' do
+    it 'should return empty string for nil' do
+      expect(markdown(nil)).to eq ''
+    end
+
+    it 'should return HTML for header markdown' do
+      expect(Redcarpet::Markdown).to receive(:new).
+        with(Redcarpet::Render::HTML, autolink: true,
+                                      space_after_headers: true,
+                                      no_intra_emphasis: true).
+        and_call_original
+
+      expect(markdown('# this is my header')).to eq "<h1>this is my header</h1>\n"
+    end
+  end
+
   describe '#registered_text' do
     describe 'returns correct string' do
       it 'when there are no registrations' do