Fixed some code that crashed in Travis build and added some test to check the functionality

app/helpers/users_helper.rb

@@ -53,7 +53,7 @@ module UsersHelper
   end
 
   def show_admin_menu?(user = nil)
-    current_administrator? || current_moderator? || current_valuator? || current_manager? || user.administrator?
+    current_administrator? || current_moderator? || current_valuator? || current_manager? || (user && user.administrator?)
   end
 
   def interests_title_text(user)

spec/features/management_spec.rb

@@ -0,0 +1,33 @@
+require 'rails_helper'
+
+feature 'Management' do
+  let(:user) { create(:user) }
+
+  scenario "Should show admin menu if logged user is admin" do
+    create(:administrator, user: user)
+    login_as(user)
+    visit root_path
+
+    expect(page).to have_link("Management")
+
+    click_link "Management"
+
+    expect(page).to have_content("My activity")
+    expect(page).to have_content("My account")
+    expect(page).to have_content("Sign out")
+  end
+
+  scenario "Should not show admin menu if logged user is manager" do
+    create(:manager, user: user)
+    login_as(user)
+    visit root_path
+
+    expect(page).to have_link("Management")
+
+    click_link "Management"
+
+    expect(page).not_to have_content("My activity")
+    expect(page).not_to have_content("My account")
+    expect(page).not_to have_content("Sign out")
+  end
+end