If you have left over rice in your Rice Cooker, make sure take it out from your Rice Cooker to avoid contamination. Because if you leave your rice there, it can contaminate bacteria in a room temperature.
I am guilty as you too that every morning when I have some left in the rice cooker, I just re-cook it and make fried rice but I didn’t know until now that it is better to remove the rice from the rice cooker. Even though we always scrub our rice cooker though it would still contaminate bacteria as the bacteria can be full grown in an overnight rice in a room temperature.
Staphylococcus and bacillus cereus is the bacteria that can be found in the rice cooker, in which it can spread all over your utensils so fast. So beware make sure that you remove the rice and do not let it stay in the rice cooker every night.