fix: type error

packages/ui/src/components/popover.tsx

@@ -116,7 +116,7 @@ export function Popover<T extends ValidComponent = "div">(props: PopoverProps<T>
 
   const content = () => (
     <Kobalte.Content
-      ref={(el: HTMLElement) => setContentRef(el)}
+      ref={(el: HTMLElement | undefined) => setContentRef(el)}
       data-component="popover-content"
       classList={{
         ...(local.classList ?? {}),