useDisplayedRowsOnly caused the data index undefined

[auntieyi]

Expected Behavior

            downloadOptions: {
                filterOptions: {
                    useDisplayedRowsOnly: true
                }
            },
            onDownload: (buildHead, buildBody, columns, data) => {
                console.log(data)
            },

Expected result like useDisplayedRowsOnly: false:
0: {index: 0, data: Array(16)}
1: {index: 1, data: Array(16)}

Current Behavior

undefined in index in current result:
0: {index: undefined, data: Array(16)}
1: {index: undefined, data: Array(16)}

Steps to Reproduce (for bugs)

1. useDisplayedRowsOnly: true
2. onDownload: (buildHead, buildBody, columns, data)
3. console.log(data)

Your Environment

Tech	Version
Material-UI	^5.0.6
MUI-datatables	^4.0.0
React	^16.14.0
browser	Chrome
etc

[auntieyi]

I found there is a bug in src/components/TableToolbar.js, and here is the quick fix for me:

diff --git a/src/components/TableToolbar.js b/src/components/TableToolbar.js
index f1d3b8b..d5fe0ba 100644
--- a/src/components/TableToolbar.js
+++ b/src/components/TableToolbar.js
@@ -154,6 +154,7 @@ class TableToolbar extends React.Component {
           row.index = index;

           return {
+            index: row.dataIndex,
             data: row.data.map(column => {
               i += 1;

Hope can apply this fix in next release. Thanks.