Fix drag n drop issue Cannot read properties of undefined (reading 'querySelector')

Closes #3467793

js/builder.js

@@ -143,11 +143,13 @@
     lpbBuilderComponent.forEach((el) => {
       const components = Array.from(el.children).filter(n => n.classList.contains('js-lpb-component'));
 
-      // Set the tabindex of the first component's up arrow to -1.
-      components[0].querySelector('.lpb-up')?.setAttribute('tabindex', '-1');
+      if (components.length > 0) {
+        // Set the tabindex of the first component's up arrow to -1.
+        components[0].querySelector('.lpb-up')?.setAttribute('tabindex', '-1');
 
-      // Set the tabindex of the last component's down arrow to -1.
-      components[components.length - 1].querySelector('.lpb-down')?.setAttribute('tabindex', '-1');
+        // Set the tabindex of the last component's down arrow to -1.
+        components[components.length - 1].querySelector('.lpb-down')?.setAttribute('tabindex', '-1');
+      }
     });
   }