keyToIndex setter fallback (#327)

Forward port this change: 1d9743b

Author: dcvz

src/components/DraggableFlatList.tsx

@@ -192,10 +192,13 @@ function DraggableFlatListInner<T>(props: DraggableFlatListProps<T>) {
 
   const renderItem: ListRenderItem<T> = useCallback(
     ({ item, index }) => {
+      const key = keyExtractor(item, index);
+      if (index !== keyToIndexRef.current.get(key)) keyToIndexRef.current.set(key, index);
+
       return (
         <RowItem
           item={item}
-          itemKey={keyExtractor(item, index)}
+          itemKey={key}
           renderItem={props.renderItem}
           drag={drag}
           extraData={props.extraData}