Problems with PHP 8.3

Unfortunately, it seems like the plugin was abandoned. I fixed the PHP 8.3 errors myself. Here are the relevant fixes (diff export):

diff --git a/includes/class.options.php b/includes/class.options.php
index f481ab3..0a0311b 100644
--- a/includes/class.options.php
+++ b/includes/class.options.php
@@ -498,7 +498,7 @@ class SLB_Options extends SLB_Field_Collection {
        function &add( $id, $properties = array(), $update = false ) {
                // Create item
                $args = func_get_args();
-               $ret  = call_user_func_array( array( 'parent', 'add' ), $args );
+               $ret  = call_user_func_array( array( 'SLB_Field_Collection', 'add' ), $args );
                return $ret;
        }
 
diff --git a/includes/class.utilities.php b/includes/class.utilities.php
index fe5d6ef..ae3db7c 100644
--- a/includes/class.utilities.php
+++ b/includes/class.utilities.php
@@ -542,9 +542,11 @@ class SLB_Utilities {
 
                // Build condition
                $sep = '.';
-               $obj = trim( $obj, $sep );
+               if ($obj !== null) {
+                       $obj = trim($obj, $sep);
+               }
                //  Strip base object
-               if ( 0 === strpos( $obj, $base . $sep ) ) {
+               if ( $obj !== null && 0 === strpos( $obj, $base . $sep ) ) {
                        $obj = substr( $obj, strlen( $base . $sep ) );
                }
                $fmt = '!!window.%1$s';