guessChangeSetId returning null will cause emails to throw exceptions

Expression commit.guessChangeSetId() is undefined on line 37, column 30 in notification-templates/BuildCompletedTextEmail.ftl.
The problematic instruction:
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==> ${commit.guessChangeSetId()} [on line 37, column 28 in notification-templates/BuildCompletedTextEmail.ftl]
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Java backtrace for programmers:
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freemarker.core.InvalidReferenceException: Expression commit.guessChangeSetId() is undefined on line 37, column 30 in notification-templates/BuildCompletedTextEmail.ftl.
	at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124)
	at freemarker.core.Expression.getStringValue(Expression.java:118)
	at freemarker.core.Expression.getStringValue(Expression.java:93)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:76)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.IteratorBlock$Context.runLoop(IteratorBlock.java:167)
	at freemarker.core.Environment.visit(Environment.java:415)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:102)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.ConditionalBlock.accept(ConditionalBlock.java:79)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:208)
	at freemarker.core.Environment.process(Environment.java:188)
	at freemarker.template.Template.process(Template.java:237)
	at com.atlassian.bamboo.ww2.BambooFreemarkerManager.renderPageWithNoContext(BambooFreemarkerManager.java:298)
	at com.atlassian.bamboo.ww2.BambooFreemarkerManager.renderPage(BambooFreemarkerManager.java:140)
	at com.atlassian.bamboo.ww2.BambooFreemarkerManager.render(BambooFreemarkerManager.java:188)
	at com.atlassian.bamboo.notification.buildcompleted.BuildCompletedNotification.getTextEmailContent(BuildCompletedNotification.java:140)
	at com.atlassian.bamboo.notification.transports.MultipartEmailTransport.sendNotification(MultipartEmailTransport.java:59)
	at com.atlassian.bamboo.notification.NotificationDispatcher.dispatchNotifications(NotificationDispatcher.java:59)
	at com.atlassian.bamboo.notification.buildcompleted.BuildCompletedNotificationListener.handleEvent(BuildCompletedNotificationListener.java:89)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
	at org.springframework.orm.hibernate.HibernateInterceptor.invoke(HibernateInterceptor.java:117)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
	at $Proxy43.handleEvent(Unknown Source)
	at com.atlassian.bamboo.event.BambooEventManager$2.run(BambooEventManager.java:46)
	at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
	at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
	at com.atlassian.bamboo.build.pipeline.concurrent.NamedThreadFactory$1.run(NamedThreadFactory.java:32)
	at edu.emory.mathcs.backport.java.util.concurrent.helpers.ThreadHelpers$1.run(ThreadHelpers.java:34)
	at java.lang.Thread.run(Thread.java:595)