FHIR Java Bug - Serialising and Deserialising

MessageTest.java

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;

import org.hl7.fhir.instance.formats.Composer;
import org.hl7.fhir.instance.formats.JsonComposer;
import org.hl7.fhir.instance.formats.JsonParser;
import org.hl7.fhir.instance.formats.ParserBase.ResourceOrFeed;
import org.hl7.fhir.instance.model.AtomFeed;
import org.junit.Test;

public class MessageTest {
	
	@Test
	public void test() throws Exception {
		// Create new Atom Feed
		AtomFeed feed = new AtomFeed();
		
		// Serialize Atom Feed
		Composer comp = new JsonComposer();
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		comp.compose(os, feed, false);
		String json = os.toString();
		
		// Deserialize Atom Feed
		JsonParser parser = new JsonParser();
		InputStream is = new ByteArrayInputStream(json.getBytes("UTF-8"));
		ResourceOrFeed result = parser.parseGeneral(is);
	}

}

OUTPUT trace

java.lang.UnsupportedOperationException: JsonNull
	at com.google.gson.JsonElement.getAsString(JsonElement.java:191)
	at org.hl7.fhir.instance.formats.JsonParserBase.parseAtom(JsonParserBase.java:118)
	at org.hl7.fhir.instance.formats.JsonParserBase.parseGeneral(JsonParserBase.java:71)
	at com.blackpear.success.inbox.message.MessageTest.test(MessageTest.java:36)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)