Error when adding images from local or persistence path to XRRefernceImageLibrary at runtime in unity

[sivamuruganszi]

Hi,
I have taken one of the example scene (ImageTrackingRuntimeSave) from the UnityARFoundationEssentials project for adding images to XRImageLibrary at runtime.

I have made some changes on that code, like instead of adding the images from unity i loaded it from persistence path, it was working fine initially. After some point of time it was giveing some issue on while adding the images to the library.
Even if i load images from my asset folder to XRImageLibrary it is give me an error.

This is the error which i am getting from the script.
System.NullReferenceException: Object reference not set to an instance of an object at DynamicLoading+<AddImage>d__6.MoveNext () [0x0009a] in

When i further debug the code its showing error in texture format line, but in my project i have made those images to Read/Write enable and format to RGBA32.

But still i am getting the error.
Could someone explain me how to solve this?