File_column intercepting send_file?

To send an image on my filesystem to a user, I have send_file in my
controller (I’m hard coding to illustrate the problem):

def sendPhoto
send_file( RAILS_ROOT + ‘/public/userPhotos/3/thumbnail.gif’,
:type=>‘image’, :disposition=>“inline”)

I get an error like I’m using a form:

TypeError (Do not know how to handle a string with value
‘thumbnail.gif’ that was passed to a file_column. Check if the form’s
encoding has been set to ‘multipart/form-data’.):
.//vendor/plugins/trunk/lib/file_column.rb:68:in assign' .//vendor/plugins/trunk/lib/file_column.rb:653:infilename=’
.//app/controllers/item_controller.rb:273:in `sendPhoto’

Why is file_column even involved here? I’m just trying to send a file
in the filesystem to the user. Why is file_column thinking I am
submitting a form?

If I comment out file_column out of my Photo class, it works fine:

Streaming file script/…/config/…/public/userPhotos/3/thumbnail.gif