Fix NullPointerException in runReadWithFilterAndAuthentication test

Relevant JIRA: https://issues.jboss.org/browse/AGDROID-37

java.lang.NullPointerException
	at org.jboss.aerogear.android.impl.pipeline.RestRunner.onReadWithFilter(RestRunner.java:185)
	at org.jboss.aerogear.android.impl.pipeline.RestAdapter$1.run(RestAdapter.java:117)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
	at java.lang.Thread.run(Thread.java:722)