Problem with gradient extraction on a sequence

Hi all,
I have had a problem using gradient extraction (polynomial, order 1) on a sequence, on macos catalina: after generating squares, if I want to remove some with the trackpad by right-clicking, SIRIL suddenly crashes ! The windows desappear, no SIRIL anymore ! What happens ???

Thanks for any answer !

Bug already tracked:

Thanx a lot!
Thierry

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