Some issues from migrating to the latest Swift programming language, I expect some further testing may delay updates to next week. The issue relates to the new language wanting explicit declaration of @objc tags, rather than implied. The prior version of the language allowed these to be implied and wouldn’t cause a crash. Easy fix, just got to make sure I have identified all of them.
Update; Unfortunately, there are a few issues with cell based table views using level indicator cells in GedGap with High Sierra and Xcode 9.2 or 9.3. Dragging or trying to change the settings of one of these cells causes Xcode to crash. I will submit a bug report to Apple but at this stage, I needs to do more investigation.