mask GUI needs much testing

Possibly crashes and other bugs when combining several masks or adding masks to different data sets.

changed milestone to %v22

added GUI release-critical labels

mentioned in issue #823 (closed)

I got malloc_consolidate(): unaligned fastbin chunk detected crash after some actions with loading and removing 2D data, but don't know how to reproduce this

closed

reopened

assigned to @m.svechnikov

mentioned in merge request !2210 (merged)

mentioned in commit fce62c8a

unassigned @m.svechnikov

No crashes are observed now, for the rest there are #878 (closed) and other issues

closed