Android ScreenShot Test Issue with Karumi Plugin

I am trying to set up a basic UI test for android using Karumi plugin https://github.com/Karumi/Shot/. However upon running ./gradlew executeScreenshotTests -Precord it always returns the following error:

execution failed for task ':app:downloadScreenshots'.
> java.io.IOException: Cannot run program "null": error=2, No such file or directory

I have read and write permissions set in the Manifest.xml file and I have a custom MyTestRunner that extends AndroidJUnitRunner that is being used for the testInstrumentationRunner in my build.gradle file

I followed all the steps in on their repo. Does anybody know what might be causing this?