fix cancel

[ozby]

we needed custom cancel button that should appear on top of layout. We didnt want to add cancel button as option. Currently, when there's no cancel button defined, clicking layout doesn't do anything and user is stucked at screen. So this fixes the issue , it closes the modal when user clicks overlay with indexNo === undefined. Also by putting this.props.children into modal, we were able to inject our own design components into by <ActionSheet><CancelButton></ActionSheet>

I believe this should come handy for other users too.