Remove link to "unauthorized" page in breadcrumb

fixes CNVS-5725

test plan:
- login as any role with admin privileges
  - click on grades from the top navigation
  - click on name in breadcrumb
  - taken to /users/#
- login as any role without admin privileges
  - click on grades from the top navigation
  - name in breadcrumb no longer has a link

Change-Id: If2495ce21371cf7b0ef468764866217567228dc7
Reviewed-on: https://gerrit.instructure.com/55526
Tested-by: Jenkins
Reviewed-by: Mark Severson <markse@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Andraia Allsop <aallsop@instructure.com>

Author: andraiaallsop

app/controllers/users_controller.rb

@@ -165,6 +165,10 @@ def grades
     @user = User.where(id: params[:user_id]).first if params[:user_id].present?
     @user ||= @current_user
     if authorized_action(@user, @current_user, :read)
+      crumb_url = polymorphic_url([@current_user]) if @user.grants_right?(@current_user, session, :view_statistics)
+      add_crumb(@current_user.short_name, crumb_url)
+      add_crumb(t('crumbs.grades', 'Grades'), grades_path)
+
       current_active_enrollments = @user.enrollments.current.includes(:course).shard(@user).to_a
 
       @presenter = GradesPresenter.new(current_active_enrollments)

app/views/users/grades.html.erb

@@ -1,7 +1,5 @@
-<% 
+<%
   content_for :page_title, join_title(t(:page_title, "Grades"), @current_user.name)
-  add_crumb(@current_user.short_name, context_url(@current_user, :context_url))
-  add_crumb(t('crumbs.grades', 'Grades'), grades_path) 
   jammit_css :user_grades
 %>