bugfix/Spesen#Index crashing
https://staging.aoz-freiwillige.ch/billing_expenses
ActionView::Template::Error (Object must be a Date, DateTime or Time object. nil given.):
ActionView::Template::Error (Object must be a Date, DateTime or Time object. nil given.):
F, [2018-04-04T14:17:49.416928 #21472] FATAL -- : [c101d7d6-5e80-49b5-9d11-29e774eeab31] 41: td= record.full_bank_details
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 42: td= link_to format_hours(record.hours.total_hours), volunteer_hours_path(record.volunteer)
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 43: td= format_currency record.amount
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 44: td= format_hours_period record.hours
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 45: td= link_to record.user, profile_link(record.user)
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 46: td= l(record.created_at.to_date)
[c101d7d6-5e80-49b5-9d11-29e774eeab31] 47:
F, [2018-04-04T14:17:49.417203 #21472] FATAL -- : [c101d7d6-5e80-49b5-9d11-29e774eeab31]
F, [2018-04-04T14:17:49.417374 #21472] FATAL -- : [c101d7d6-5e80-49b5-9d11-29e774eeab31] app/helpers/format_helper.rb:13:in `format_hours_period'
[c101d7d6-5e80-49b5-9d11-29e774eeab31] app/views/billing_expenses/index.html.slim:44:in `block in _app_views_billing_expenses_index_html_slim___2103386005377330170_47453746246920'
[c101d7d6-5e80-49b5-9d11-29e774eeab31] app/views/billing_expenses/index.html.slim:31:in `_app_views_billing_expenses_index_html_slim___2103386005377330170_47453746246920'