Humanize only the type parameter

The project parameter does not need to be humanized.

When no type or filter project are selected, show 'Unread' instead of
'Inbox', to be consistent with the names of the filters.

src/api/app/views/webui/users/notifications/index.html.haml

@@ -8,7 +8,7 @@
     .card.mb-3
       %strong.d-block.d-md-none.p-3{ data: { toggle: 'collapse', target: '#filters' },
                                   aria: { expanded: true, controls: 'filters' } }
-        Filtered by: #{(params[:type] || params[:project] || 'Inbox').humanize}
+        Filtered by: #{params[:type]&.humanize || params[:project] || 'Unread'}
         %i.float-right.mt-1.fa.fa-chevron-down
       .card-body.collapse#filters
         = render partial: 'notifications_filter', locals: { projects_for_filter: @projects_for_filter, notifications_count: @notifications_count }