This is not something that has to be fixed by the dev but a warning to iOS beta users.
After updating iOS to beta 6 the "system" gestures actions are performed in place of Artstudio's ones. Here's some examples
2 finger tap is working as intended as there's no iOS gesture with 2 fingers.
3 finger tap displays a "nothing to undo" popup or the text edit popup (the rounded new one including cut, copy and so on)
4 finger tap works as intended if performed just after a triple tap, otherwise it does nothing.
Undo and redo buttons do work though, so the issue is caused by the system registering text gestures even without text fields.
