Undefined variables

Hi. We have an error with the plugin NC Chart. On activation, we have Notices about Undefined variable, index on lines 272, 273, 361, 311.

Could you help me? Thank you!!!

Here the code lines :
Notice: Undefined variable: id in /home/francish/public_html/alexetmarie/wp-content/plugins/productsize-chart-for-woocommerce/public/class-productsize-chart-public.php on line 272

Notice: Undefined index: button-position in /home/francish/public_html/alexetmarie/wp-content/plugins/productsize-chart-for-woocommerce/public/class-productsize-chart-public.php on line 273

Notice: Undefined variable: id in /home/francish/public_html/alexetmarie/wp-content/plugins/productsize-chart-for-woocommerce/public/class-productsize-chart-public.php on line 361

Notice: Undefined variable: id in /home/francish/public_html/alexetmarie/wp-content/plugins/productsize-chart-for-woocommerce/public/class-productsize-chart-public.php on line 311

https://wordpress.org/plugins/productsize-chart-for-woocommerce/