3D FlipBook - Update appears to have problems. Steps to reproduce: Deleted plugin. Added plugin back. Deleted all books. Create book base

Update appears to have problems.

Steps to reproduce: Deleted plugin. Added plugin back. Deleted all books. Create book base on pdf. Hit Publish:

Warning: Invalid argument supplied for foreach() in /websites/123reg/LinuxPackage22/sy/st/em/system-development.co.uk/public_html/cherita/wp-content/plugins/3d-flip-book/inc/post-pages.php on line 18

Warning: Invalid argument supplied for foreach() in /websites/123reg/LinuxPackage22/sy/st/em/system-development.co.uk/public_html/cherita/wp-content/plugins/3d-flip-book/inc/post-pages.php on line 153

Warning: Cannot modify header information – headers already sent by (output started at /websites/123reg/LinuxPackage22/sy/st/em/system-development.co.uk/public_html/cherita/wp-content/plugins/3d-flip-book/inc/post-pages.php:18) in /websites/123reg/LinuxPackage22/sy/st/em/system-development.co.uk/public_html/cherita/wp-includes/pluggable.php on line 1195