Fix media gallery items having incorrect borders when hidden (#32257)

app/javascript/mastodon/components/media_gallery.jsx

@@ -336,14 +336,14 @@ class MediaGallery extends PureComponent {
 
     return (
       <div className={`media-gallery media-gallery--layout-${size}`} style={style} ref={this.handleRef}>
+        {children}
+
         {(!visible || uncached) && (
           <div className={classNames('spoiler-button', { 'spoiler-button--click-thru': uncached })}>
             {spoilerButton}
           </div>
         )}
 
-        {children}
-
         {(visible && !uncached) && (
           <div className='media-gallery__actions'>
             <button className='media-gallery__actions__pill' onClick={this.handleOpen}><FormattedMessage id='media_gallery.hide' defaultMessage='Hide' /></button>