Avoid CLS issue on mobile #10305

On mobile the menu is closed by default. Before, it was opened, then
very quickly closed. That leads to a huge Cumulative Layout Shift issue.

On http://localhost:4201/, Lighthouse reported a CLS of 0.343,
now it is 0.

projects/natural/src/lib/modules/sidenav/sidenav.service.ts

@@ -195,7 +195,11 @@ export class NaturalSidenavService extends NaturalAbstractController {
         assert(this.openedStorageKeyWithName);
         const value = this.sessionStorage.getItem(this.openedStorageKeyWithName);
 
-        return value === null || value === 'true';
+        if (value === null) {
+            return !this.isMobileView();
+        } else {
+            return value === 'true';
+        }
     }
 
     /**