I am sure you will get lots of advice on this one, my two penneth for what it is worth, seal the entrance immediately to prevent robbing and that will give you time to consider your options. I had a nuc which had predictably died, I left the cleaning until this last week when I removed all the dead bees and debris, within a day it was being visited by my other girls from adjacent hives, I had a similar situation when I removed a queen from a week nuc, it almost immediately got the attention of robbers. I suspect it is the lack of queen pheremone that triggers the reaction.