long raw datatype

How do you check if a long raw datatype IS NULL?

I get an error when I compile the following code:

  IF :bpms_thumbnails.thumbnail_image IS NULL THEN     error_str := error_str || '- Thumbnail Image'||chr(10);   END IF; Error 49 at line 32, column 6
bad bind variable 'bpms_thumbnails.thumbnail_image'

I'm working with Oracle 7.3 and Forms 4.5. Received on Wed Mar 22 2000 - 08:46:19 CST