Updating a fact causes NPE with extends

Problem: When there are two rules (A and B) such that B extends A and both A and B reference the same fact in their conditions, calling update on that fact after calling fireAllRules causes a NPE.

DRL:

package inheritance

import org.drools.Address

rule "Parent"
	enabled false
	when
		Address(suburb == "xyz")
	then
	
end

rule "Child" extends "Parent"
	when
		$addy:Address(street == "123 some street")
		
	then
		System.out.println($addy);
end

Test:

package org.drools.testframework;

import org.drools.Address;
import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.io.Resource;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;
import org.drools.runtime.rule.FactHandle;
import org.junit.Test;

public class ExternalUpdateInheritanceTest {

	@Test
	public void testExternalInheritanceFactUpdates() {
		KnowledgeBase knowledgeBase = null;

		KnowledgeBuilder builder = KnowledgeBuilderFactory.newKnowledgeBuilder();

		Resource newClassPathResource = ResourceFactory.newClassPathResource("org/drools/lang/inheritance.drl");
		builder.add(newClassPathResource, ResourceType.DRL);

		if (builder.hasErrors()) {
			throw new RuntimeException(builder.getErrors().toString());
		}
		knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase();
		knowledgeBase.addKnowledgePackages(builder.getKnowledgePackages());
		
		StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession();
		
		Address address = new Address();
		
		address.setSuburb("xyz");
		FactHandle addressHandle = ksession.insert(address);
		
		int rulesFired = ksession.fireAllRules();
		
		address.setStreet("123 some street");
		
		
		ksession.update(addressHandle, address);
		
		System.out.println(rulesFired);
	}
}

Stack Trace:
java.lang.NullPointerException
at org.drools.common.DefaultAgenda.createActivation(DefaultAgenda.java:572)
at org.drools.reteoo.RuleTerminalNode.modifyLeftTuple(RuleTerminalNode.java:297)
at org.drools.reteoo.LeftTupleSource.doModifyLeftTuple(LeftTupleSource.java:297)
at org.drools.reteoo.AbstractTerminalNode.modifyLeftTuple(AbstractTerminalNode.java:104)
at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateModifyLeftTuple(SingleLeftTupleSinkAdapter.java:205)
at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateModifyObject(SingleLeftTupleSinkAdapter.java:235)
at org.drools.reteoo.LeftInputAdapterNode.modifyObject(LeftInputAdapterNode.java:170)
at org.drools.reteoo.SingleObjectSinkAdapter.propagateModifyObject(SingleObjectSinkAdapter.java:68)
at org.drools.reteoo.AlphaNode.modifyObject(AlphaNode.java:157)
at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:507)
at org.drools.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:421)
at org.drools.reteoo.ObjectTypeNode.modifyObject(ObjectTypeNode.java:314)
at org.drools.reteoo.EntryPointNode.modifyObject(EntryPointNode.java:265)
at org.drools.common.NamedEntryPoint.update(NamedEntryPoint.java:474)
at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:960)
at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:933)
at org.drools.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:284)
at org.drools.testframework.ExternalUpdateInheritanceTest.testExternalInheritanceFactUpdates(ExternalUpdateInheritanceTest.java:44)