FATAL ERROR – BULK OPTIMIZATION

I was in the media library and selected a number of photos and pdfs and then select a “bulk action” to optimize the selected objects and hit apply. I received this fatal error.
(please note that the images and pdfs were optimized (?) if with the error????

Error Details
=============
An error of type E_ERROR was caused in line 649 of the file /home/nhwgao5/public_html/testbed9051/wp-content/plugins/shortpixel-image-optimiser/class/wp-short-pixel.php. Error message: Uncaught Error: Cannot use string offset as an array in /home/nhwgao5/public_html/testbed9051/wp-content/plugins/shortpixel-image-optimiser/class/wp-short-pixel.php:649
Stack trace:
#0 /home/nhwgao5/public_html/testbed9051/wp-includes/class-wp-hook.php(286): WPShortPixel->handleCustomBulk(”)
#1 /home/nhwgao5/public_html/testbed9051/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(”, Array)
#2 /home/nhwgao5/public_html/testbed9051/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#3 /home/nhwgao5/public_html/testbed9051/wp-admin/admin.php(365): do_action(‘load-upload.php’)
#4 /home/nhwgao5/public_html/testbed9051/wp-admin/upload.php(10): require_once(‘/home/nhwgao5/p…’)
#5 {main}
thrown