Add missing key to span element

src/Components/ElementsList/ElementsList.tsx

@@ -202,6 +202,7 @@ function ElementsListRow(
   for (let i = 0; i < depth; i++) {
     verticalBars.push(
       <span
+        key={`${key}-${i}`}
         className={`h-full border-l-2 pr-2 ${verticalBarSelectedClass}`}
       ></span>
     );