RAM for History of FFT never gets freed

[preamp-org]

I have noticed this using the FFT on ridiculously high memory depths and an acquisition time of around 2 seconds. With the History depth set to a standard of 10, I can cleary observe the RAM usage rise with every acquisition. Once those 10 history slots have been filled up, the RAM usage will stay high at that level, even if I reduce the History depth to 1 afterwards. Setting it to 20 instead will lead to another increase in RAM usage, from the former 10-level to the level of 20 now. Again, it will stay at that level, even if I reduce the History depth back down.
I think that the unneccessary RAM should be freed on reducing the History size. It should not be purged everytime the History depth is changed, because you'd want to keep your history on setting a higher value, but there's no need to keep the RAM occupied when setting a lower value or even disable History altogether.