bugzid 9279: fixing an NPE in java client

Fix for the following NPE:

java.lang.NullPointerException: null
	at com.sailthru.client.exceptions.ApiException.create(ApiException.java:38)
	at com.sailthru.client.http.SailthruHandler.handleResponse(SailthruHandler.java:70)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:945)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:919)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:910)