illegal string offset id php error

Hi there my wordpress site page: http://www.localsworld.com/map/ is showing the error warning: illegal string offset ‘id’ in my interactive world maps plug in – the line it refers to in the interactive world maps php (111) is written as:
$id = $atts[‘id’];

please – how can I change the coding to remove the error? Thanks!

https://ww.wp.xz.cn/plugins/interactive-world-map/