insert/cut frame is not constrained to the canvas size.
edited March 2017
Steps to reproduce:
1. add a new animation
2. select the front edge of the last frame on the canvas (as shown in the gif)
3. left-click to insert new frame
at the ninth tile, the tool should stop inserting more frames. That or it should make the canvas bigger.
The tool doesn't care about how many tiles the canvas consists of.