Why does the check_box form helper generate two checkboxes, one hidden?
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this code:
    =form_fo :store_products do |f|
      = f.check_box :track_inventory

creates this html:

    <input name="product_group[products_attributes][0][store_products_attributes}[1342647745501][track_inventory]" type="hidden" value="0">
    
    <input id="product_group_products_attributes_0_store_products_attributes_1342647745501_track_inventory" name="product_group[products_attributes][0][store_products_attributes][1342647745501][track_inventory]" type="checkbox" value="1">
What is the reason for the first hidden element?

