Really? I was doing this over and over when I played as Czechslovakia after I got the first one just to make sure it was reproducible. The remove brigade button wasn't unavailable/greyed out on the division with no brigades (it was a division with more than 1 brigade type available, division may or may not have been converted in type, don't remember) and every click would add a (Null) brigade type to the redeployment pool.