fix error line

src/components/ai-assistant/PromptInput.jsx

@@ -17,6 +17,7 @@ import { cn } from '@/lib/utils';
  * gain — the suggestion chips already teach the range of what can be asked, and
  * they do it without a timer or a rerender every four seconds.
  */
+/** @param {any} props */
 export function PromptInput({
   value,
   onChange,
@@ -26,7 +27,7 @@ export function PromptInput({
   placeholders = ['Ask anything…'],
   autoFocus = false,
   align = 'left',
-  className,
+  className = '',
 }) {
   const textareaRef = React.useRef(null);
   const [focused, setFocused] = React.useState(false);