Fix TypeScript error in Webamp renderInto call

Add non-null assertion operator to ref.current when calling webamp.renderInto()
to match the pattern used elsewhere in the component and resolve the CI type error:
"Argument of type 'HTMLDivElement | null' is not assignable to parameter of type 'HTMLElement'"

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: captbaritone

packages/skin-database/app/(modern)/scroll/Webamp.tsx

@@ -42,7 +42,7 @@ export default function WebampComponent({
 
       webamp.onClose(closeModal);
       // ref.current!.style.opacity = "0";
-      await webamp.renderInto(ref.current);
+      await webamp.renderInto(ref.current!);
       const { width } = outerRef.current!.getBoundingClientRect();
       const zoom = width / SCREENSHOT_WIDTH;
       document