Set marginRight as string (#24422)

app/javascript/mastodon/containers/media_container.jsx

@@ -54,7 +54,7 @@ export default class MediaContainer extends PureComponent {
 
   handleCloseMedia = () => {
     document.body.classList.remove('with-modals--active');
-    document.documentElement.style.marginRight = 0;
+    document.documentElement.style.marginRight = '0';
 
     this.setState({
       media: null,

app/javascript/mastodon/features/ui/components/modal_root.jsx

@@ -73,7 +73,7 @@ export default class ModalRoot extends React.PureComponent {
       document.documentElement.style.marginRight = `${getScrollbarWidth()}px`;
     } else {
       document.body.classList.remove('with-modals--active');
-      document.documentElement.style.marginRight = 0;
+      document.documentElement.style.marginRight = '0';
     }
   }