Getting Run time exception

[KhadkaRabindra]

Fatal Exception: java.lang.RuntimeException
An error occured while executing doInBackground()
android.os.AsyncTask$3.done

Caused by java.lang.NullPointerException
Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference
com.ice.restring.StringsLoaderTask.doInBackground

com.ice.restring.StringsLoaderTask.doInBackground (StringsLoaderTask.java:36)
com.ice.restring.StringsLoaderTask.doInBackground (StringsLoaderTask.java:16)
android.os.AsyncTask$2.call (AsyncTask.java:292)
java.util.concurrent.FutureTask.run (FutureTask.java:237)
java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1112)
java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:587)
java.lang.Thread.run (Thread.java:818)