I copied data from preview and visited http://transition.dev.gov.uk/sites/civilservice/mappings?sort=by_hits and this happened:
```
undefined method `zero?' for nil:NilClass
app/models/mapping.rb:115:in `hit_percentage'
app/views/mappings/_mappings_table.html.erb:65:in `block (2 levels) in _app_views_mappings__mappings_table_html_erb___2965527058308090296_70343114093080'
app/views/mappings/_mappings_table.html.erb:40:in `block in _app_views_mappings__mappings_table_html_erb___2965527058308090296_70343114093080'
app/views/mappings/_mappings_table.html.erb:11:in `_app_views_mappings__mappings_table_html_erb___2965527058308090296_70343114093080'
app/views/mappings/index.html.erb:30:in `_app_views_mappings_index_html_erb___1080042371542041461_70343075534280'
```