Update apps/demos/Demos/DropDownBox/SingleSelection/ReactJs/App.js

Co-authored-by: Copilot <[email protected]>
Signed-off-by: assylbek.danyshbek <[email protected]>

Author: DuckTieCorpMember

apps/demos/Demos/DropDownBox/SingleSelection/ReactJs/App.js

@@ -39,7 +39,9 @@ function App() {
 
   const treeViewOnContentReady = useCallback(
     (e) => {
-      e.component.selectItem(treeBoxValue);
+      if (treeBoxValue) {
+        e.component.selectItem(treeBoxValue);
+      }
     },
     [treeBoxValue],
   );