Fix for bug 2398: Source of Classification - Add item or Edit item in

Fix for bug 2398: Source of Classification - Add item or Edit item in
staff client is defaulting to the ASNCR code instead of the blank above

For some reason the loop used to build the list of values was
setting the first value to the $value variable if $value wasn't
set already, and the default_value was inside rather than outside
the loop. I've removed the setting inside the loop and placed
the default value outide the loop. It's possible I just don't
understand what the original intention was.