Delete and Pull · cmd ⌫ on artboard causes sketch crash
steps to reproduce:
- create artboard
- select artboard
- hit [CDM] + [BACKSPACE]
- hit [A]
- drag to create new artboard

demo:
https://www.dropbox.com/s/ab6lyw7vjtt3zlw/sketch_sketch%20crash_20151104.mov?dl=0
