Copy should be disabled when nothing is on the canvas

[fsih]

Expected Behavior

Copy doesn't do anything when nothing is on the canvas, so it should probably be disabled. We would need new state to track whether the canvas is empty, which is potentially expensive in bitmap.

Actual Behavior

Copy is currently always enabled

[carljbowman]

It does seem like Copy should be disabled if there is no artwork on the canvas. Did you have alternatives in mind @fsih?