Not working when `vue-avatar-cropper` is inside of a modal.

[Troy]

Thanks for this great plugin!

I've been working on this issue for a couple of hrs now. When I add vue-avatar-cropper inside of a modal, it doesn't work properly. It works fine without a modal. Click on the modal "Launch demo modal" button, then try to add/load a foto. There are no console errors nothing.

I was able to duplicate the issue below.
https://codesandbox.io/s/gracious-snow-qnce4

Thank you

[安正超]