fix: get updated index after updateBeforeSortStart

In the event that the node’s index changes during updateBeforeSortStart, we need to make sure to get the latest value for the index of the node currently being sorted

Author: Clauderic Demers

src/SortableContainer/index.js

@@ -226,18 +226,20 @@ export default function sortableContainer(
         } = this.props;
 
         const {node, collection} = active;
-        const {index} = node.sortableInfo;
 
         if (typeof updateBeforeSortStart === 'function') {
           this._awaitingUpdateBeforeSortStart = true;
 
           try {
+            const {index} = node.sortableInfo;
             await updateBeforeSortStart({collection, index, node}, event);
           } finally {
             this._awaitingUpdateBeforeSortStart = false;
           }
         }
 
+        // Need to get the latest value for `index` in case it changes during `updateBeforeSortStart`
+        const {index} = node.sortableInfo;
         const margin = getElementMargin(node);
         const containerBoundingRect = this.scrollContainer.getBoundingClientRect();
         const dimensions = getHelperDimensions({collection, index, node});