SELECT 
  cscart_languages.* 
FROM 
  cscart_languages 
  LEFT JOIN cscart_storefronts_languages AS storefronts_languages ON storefronts_languages.language_id = cscart_languages.lang_id 
WHERE 
  1 
  AND (
    storefronts_languages.storefront_id = 1 
    OR storefronts_languages.storefront_id IS NULL
  )

Query time 0.00012

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE storefronts_languages system PRIMARY,idx_storefront_id 0 Const row not found
1 SIMPLE cscart_languages ALL 1

Result

lang_code name status country_code lang_id
en English A EN 1