Fix issues editing artificial horizon.

This small MR fixes 2 issues related to editing of the Artificial Horizon feature.

How to reproduce the bugs

Using the master branch:

Start with no artificial horizons defined. That is, open KStars, go to Settings --> Artificial Horizon, and there should be nothing populating the table.

Make a first region

• Click on '+' Add Region.
• Click on Select Points from the SkyMap (button on far right)
• Make a Region with 5 points (you should have a checkbox now--if not add a point on the start until you do).
• Click on Apply
• You should see one region defined in the table, named 'Region 1'

Make a second region

• Click on '+' Add Region.
• Click on Select Points from the SkyMap (button on far right)
• Make a Region with 5 points (you should have a checkbox now--if not add a point on the start until you do).
• Click on Apply
• You should see two regions defined in the table, named 'Region 1' and 'Region 2' Click on Save Regions (the disk).

Bug 1

Quit KStars now, and relaunch, and look at Settings --> Artificial Horizon, you should see a 3rd region (named '0') in the table. https://photos.app.goo.gl/og4zSjWyZXruQmdK9

Bug 2

• Delete all the regions, and save.
• Restart make sure they're all really gone.
• Repeat the procedure above, starting from 'Start with no artificial horizons defined' through 'Click on Save Regions (the disk)'.
• At this point, click on Region 1 in the Regions Table and you should see it has 5 points (assuming you made it with 5),
• Click on Region 2, and you also see 5 points (assuming you made it that way).
• Now click on 'Region 1' again, and click '-' (Remove Region). Region 1 should go away.
• Now click on 'Region 2'. Note that it only has 4 points (or 1 fewer than you defined). It should still have 5 (or the same number you defined earlier).

Repeat all of the above using this MR. You should find that the issues are fixed.