Open a raw file, develop it and then either save or don't save the file. Go back to the Develop persona and choose the white balance tool (actually any tool) and the picture disappears. If you try and leave the Develop Persona you are presented with a window asking if you would like to cancel the development or accept it. Cancelling does nothing and developing causes the crash. 
Metal on or off makes no difference. Other than Open GL seems slower for the initial development, the tool chosen doesn't get selected and has no effect but the image will disappear.
Odd little detail is that the Develop and Cancel buttons are missing in the recipe (process raw, go back to develop persona) to make it crash.
Activity monitor shows no real activity happening.   This is normal ... ------------------------------ ---------------------- This is heading for a crash... -------------------------------------------------------------