remove Preview notice header when no previews (github#25785)

Author: rachmari

components/rest/PreviewsRow.tsx

@@ -9,6 +9,7 @@ type Props = {
 
 export function PreviewsRow({ slug, hasRequiredPreviews, xGitHub }: Props) {
   const { t } = useTranslation('products')
+  const hasPreviews = xGitHub.previews && xGitHub.previews.length > 0
 
   return (
     <tr>
@@ -24,7 +25,7 @@ export function PreviewsRow({ slug, hasRequiredPreviews, xGitHub }: Props) {
           <p className="m-0">
             Setting to
             <code>application/vnd.github.v3+json</code> is recommended.
-            {xGitHub.previews && (
+            {hasPreviews && (
               <a href={`#${slug}-preview-notices`} className="d-inline">
                 {xGitHub.previews.length > 1
                   ? ` ${t('rest.reference.see_preview_notices')}`

components/rest/RestPreviewNotice.tsx

@@ -21,7 +21,7 @@ export function RestPreviewNotice({ slug, previews }: Props) {
     )
   })
 
-  return (
+  return previews.length > 0 ? (
     <>
       <h4 id={`${slug}-preview-notices`}>
         {previews.length > 1
@@ -30,5 +30,5 @@ export function RestPreviewNotice({ slug, previews }: Props) {
       </h4>
       {previewNotices}
     </>
-  )
+  ) : null
 }