Bug 457615

**SUMMARY**
In the menu 'StellarSolver Options' > 'Alignment Options' toggling the 'Overlay' checkbox has no effect unless KStars full shutdown. Only after KStars restart the overlay image becomes in/visible as selected by the checkbox.

**STEPS TO REPRODUCE**
1. Start plate solving (Simulator is sufficient)
2. When an overlay image is visible on the KStars star map (default), deactivate the 'Overlay' option in 'StellarSolver Options' > 'Alignment Options' > 'Overlay' checkbox. The overlay image still remains visible.
3. Close KStars completely and restart it. The 'Overlay' is now(!) turned off during plate solving and afterwards.
4. Activate the 'Overlay' check box again > immediately(!) the 'Overlay' image appears on the KStars star map.
5. BUG: Disabling this option now(!) has no(!) effect -the 'Overlay' image remains visible.
6. Repeat from step '2.' to reproduce everything as described.

**OBSERVED RESULT**
After switching off (deactivate) the 'Overlay' image, KStars has to be shutdown completely and then to be restarted (losing the whole work in progress, of course). The 'Overlay' image becomes unvisible only after 'rebooting' KStars.

Even more strange: When KStars was restarted this way (with 'Overlay' being disabled before), the Overlay can be instantly activated again with a single click on its checkbox. The 'Overlay' is now visible but cannot be switched invisible again without a full KStars restart.

**EXPECTED RESULT**
Switching 'Overlay' image on/off should be instantly effective, at least after pressing [OK] in the options dialog.

**SOFTWARE/OS VERSIONS**
 - OS: current Astroberry on RasPi4
 - KStars-3.5.9 Stable
 - Build: 2022-06-04T11:30:31Z