fix safari sidebar overflow

Signed-off-by: JPeer264 <jan.oster94@gmail.com>

.changeset/real-sheep-chew.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core-components': minor
+---
+
+Fix the hidden sidebar's submenu when the sidebar is scrollable

packages/core-components/src/layout/Sidebar/Bar.tsx

@@ -41,15 +41,21 @@ import { coreComponentsTranslationRef } from '../../translation';
 export type SidebarClassKey = 'drawer' | 'drawerOpen';
 const useStyles = makeStyles<Theme, { sidebarConfig: SidebarConfig }>(
   theme => ({
-    drawer: {
-      display: 'flex',
-      flexFlow: 'column nowrap',
-      alignItems: 'flex-start',
-      position: 'fixed',
+    root: {
       left: 0,
       top: 0,
       bottom: 0,
       zIndex: theme.zIndex.appBar,
+      position: 'fixed',
+    },
+    drawer: {
+      display: 'flex',
+      flexFlow: 'column nowrap',
+      alignItems: 'flex-start',
+      left: 0,
+      top: 0,
+      bottom: 0,
+      position: 'absolute',
       background: theme.palette.navigation.background,
       overflowX: 'hidden',
       msOverflowStyle: 'none',