bug fix #400265: meridian flip check before capturing

Summary: Meridian flips are also initiated if a sequence has only one single frame captured. This resolves bug #400265

Test Plan:

1. Create a sequence with one single light frame and select "Meridian flip if HA > xx".
2. Create a schedule with a target close before meridian using the sequence above that repeats the sequence endlessly.
3. Start the schedule.

Expected result: as soon as the meridian is passed, a meridian flip is executed. After a successful meridian flip, capturing is continued.

Reviewers: TallFurryMan, mutlaqja

Reviewed By: TallFurryMan, mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D17159