v1.49a - Duplicate Layer fix

Just a quick hotfix for a crash that only occurred in release builds of PixelCNC when duplicating a selected layer. This wasn't occurring in debug builds and was difficult to track down as a result. I personally use the duplicate layer function quite a bit so I felt it warranted an entire release in this case, rather than sitting on it until enough fixes accumulated to package together.

Doing some CNC recording today to finish editing the Basic Relief Carving tutorial video. Stay tuned!