Please see the error message while login as students :
RuntimeError in User#dashboard
Showing app/views/user/dashboard.erb where line #30 raised:

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

Extracted source (around line #30):

27:
28: <% elsif @user.student? %>
29:
30: <%= link_to "", {:controller => "student", :action => "profile", :id => @student.id},
31: :class => "option_buttons", :id => "student_details_button", :title => " View your profile." %>
32: <%= link_to "", {:controller => "news", :action => "index"},
33: :class => "option_buttons", :id => "campus_news_button",:title => "Search for news/announcements"%>