Unable to export last asset as PNG out of a selection!

Hi

I had wrote a script to export my selection as PNG through asset export. But the last selection is not exporting as PNG throwing an error. When it comes to SVG in the same script its working fine. Ill paste the sample script here, please correct me if I had committed some mistake.

I reiterate SVG export working fine in below script its only problem with PNG.

var doc = app.activeDocument;

var selectedObjects = doc.selection;

//remove all assets

if (doc.assets.length>0){

doc.assets.removeAll();

}

//Adding selection to assets panel

for (var i=0; i<selectedObjects.length; i++){

     var currentObject = selectedObjects;

     doc.selection = currentObject;

     var currentAsset = doc.assets.addFromSelection ();

     currentAsset.assetName = currentObject.name;

}

//Collecting new assets

var assets = doc.assets;

//Query Asset ID's

var assetArray = [];

for (var z=0; z<assets.length; z++){

    assetArray=assets.assetID;

    }

//Creation of destination folder

var destFolder = Folder("C:/Users/Xxxxx/Desktop/script/export/Icon_01");

if(!destFolder.exists) destFolder.create();

//Defining assets to export

var whatToExport = new ExportForScreensItemToExport();

whatToExport.assets = assetArray;

whatToExport.artboards ="";

//As SVG

var svgParams = new ExportForScreensOptionsWebOptimizedSVG();

doc.exportForScreens(destFolder, ExportForScreensType.SE_SVG, svgParams, whatToExport);

//As PNG

var pngParams = new ExportForScreensOptionsPNG24();

doc.exportForScreens(destFolder, ExportForScreensType.SE_PNG24, pngParams, whatToExport);

alert('done');