Now that you cleared the drains, try Einszett Klima-Cleaner AC Odor Remover to kill the stuff causing the odor.

 

And turn on the fan once in awhile to clear out any moisture that will grow/smell again.

 

I have been running the fan on manual full time. It doesn't smell bad now but I may try "Einszett Klima-Cleaner AC Odor Remover"( thanks Acamato) Just to freshen it up a bit. Still not sure how critical it is to replace the "Broken Nipple" I would think it would be much better if it was there. Now I must find one.