refactor: Fix undefined className in ListItem

app/components/ui-lib.tsx

@@ -42,7 +42,7 @@ export function ListItem(props: {
   className?: string;
 }) {
   return (
-    <div className={styles["list-item"] + ` ${props.className}`}>
+    <div className={styles["list-item"] + ` ${props.className || ""}`}>
       <div className={styles["list-header"]}>
         {props.icon && <div className={styles["list-icon"]}>{props.icon}</div>}
         <div className={styles["list-item-title"]}>