Undo/Redo button cause application error

[vshakitskiy]

Making undo/redo using Ctrl + z/Z works fine. But, using undo button on the left pannel cause application error. Here's the console:

[QuiiBz]

Yeah I've seen that one, it's so strange. Works perfectly fine with ctrl+z/Z but doesn't on the buttons 🤯

[vshakitskiy]

If we place undo/redo functions inside another function, it won't cause an error:

[vshakitskiy]

Fixed in #52