What are the possible causes?

( ! ) Notice: Undefined property: stdClass::$ID
in *****/wp-content/plugins/css-javascript-toolbox/access.points/metabox.accesspoint.php on line 56
Call Stack
# Time Memory Function Location
1 0.0003 136700 {main}( ) …/link-add.php:0
2 1.4438 23562792 include( ‘*****/wp-admin/edit-link-form.php’ ) …/link-add.php:27
3 1.4496 23759396 do_action( ) …/edit-link-form.php:34
4 1.4506 23762896 call_user_func_array:{*****/wp-includes/plugin.php:525} ( ) …/plugin.php:525
5 1.4506 23762980 CJTMetaboxAccessPoint->postsMetabox( ) …/plugin.php:525

( ! ) Notice: Trying to get property of non-object
in *****/wp-content/plugins/css-javascript-toolbox/models/metabox.php on line 104
Call Stack
# Time Memory Function Location
1 0.0003 136700 {main}( ) …/link-add.php:0
2 1.4438 23562792 include( ‘*****/wp-admin/edit-link-form.php’ ) …/link-add.php:27
3 1.4496 23759396 do_action( ) …/edit-link-form.php:34
4 1.4506 23762896 call_user_func_array:{*****/wp-includes/plugin.php:525} ( ) …/plugin.php:525
5 1.4506 23762980 CJTMetaboxAccessPoint->postsMetabox( ) …/plugin.php:525
6 1.4520 23764572 CJTAccessPoint->route( ) …/metabox.accesspoint.php:58
7 1.4520 23764644 CJTController::getInstance( ) …/access-point.class.php:213
8 1.4520 23764644 CJTController::create( ) …/controller.inc.php:222
9 1.4567 23843016 CJTMetaboxController->__construct( ) …/controller.inc.php:184
10 1.4610 23872788 CJTMetaboxModel->doPost( ) …/metabox.php:40

https://wordpress.org/plugins/css-javascript-toolbox/