Stranger and stranger. I've looked at it again and I'm still seeing it in 1.6.0.160
Clearly there was some intermediate step that I didn't realise was making a difference. This time I was able to reproduce this repeatedly.
This time I opened an image, hit the duplicate layer button, then closed the image without saving.
The menu items are not disabled and cause the exceptions.
Stranger and stranger.
I've looked at it again and I'm still seeing it in 1.6.0.160
Clearly there was some intermediate step that I didn't realise was making a difference. This time I was able to reproduce this repeatedly.
This time I opened an image, hit the duplicate layer button, then closed the image without saving.
The menu items are not disabled and cause the exceptions.