= f.field_container :shipping_categories do 
  = f.label :shipping_category_id, t(:shipping_category)
  = f.collection_select(:shipping_category_id, Spree::ShippingCategory.all, :id, :name, {:include_blank => true}, {:class => 'select2 fullwidth'})
  = f.error_message_on :shipping_category_id

= f.field_container :shipping_categories do 
  = f.label :shipping_category_id, t(:shipping_category)
  = f.collection_select(:shipping_category_id, Spree::ShippingCategory.all, :id, :name, {:include_blank => false}, {:class => 'select2 fullwidth'})
  = f.error_message_on :shipping_category_id

Remove blank option from shipping category dropdown
Remove blank option from shipping category dropdown
