GUI: changing scan parameters has no effect upon simulation

Probably this error has slipped in through my recent deep refactoring.

added GUI bug release-critical labels

assigned to @j.wuttke

assigned to @m.svechnikov and unassigned @j.wuttke

mentioned in issue #340 (closed)

mentioned in merge request !1457 (merged)

mentioned in commit 66370b38

closed with merge request !1457 (merged)