Dashboard stopped working. Error when accessing dashboard is "divided by 0", in trace is:

ZeroDivisionError
divided by 0
app/helpers/dashboard_helper.rb:8:in `/'
app/helpers/dashboard_helper.rb:8:in `count_reports'
app/views/dashboard/index.html.erb:40:in `_app_views_dashboard_index_html_erb___1264836471_70197812643080_0'
app/controllers/dashboard_controller.rb:6:in `index'
lib/foreman/threadsession.rb:31:in `clear_thread'

Other tabs like hosts, reports, facts, etc. is working like as usual.