Aquí está una subrutina para la sustitución de caracteres:
on replace_chars(this_text, search_string, replacement_string)
set AppleScript's text item delimiters to the search_string
set the item_list to every text item of this_text
set AppleScript's text item delimiters to the replacement_string
set this_text to the item_list as string
set AppleScript's text item delimiters to ""
return this_text
end replace_chars
Fuente: http://www.macosxautomation.com/applescript/sbrt/sbrt-06.html
Entre estas dos líneas de AppleScript, inserte el siguiente:
set search to replace_chars(search," ","+")