17.17-beta2 Roll Confirmation #2030, multiple issues

[devakm]

1. Appears to not support .webm token art. Tokens using a .png file work but .webm doesn't.

2. Max Actions and Maneuver checks seem unreliable.

3. Cancel button does not in fact cancel the action if using an OtF. It just causes the failure clause to trigger. You can see this result in the screenshot. I clicked cancel and got my OtF message "Your attack missed!" from the f:{failureclause}.