Exception rendering ticket after deleting priority

A ticket was created with a priority which was later deleted. I edited the ticket to change the priority to one that would exist after the deletion, then deleted the priority. A user reported the following error:

An error occurred whilst rendering this message. Please contact the administrators, and inform them of this bug.

Details:
-------
org.apache.velocity.exception.MethodInvocationException: Invocation of method 'printChangelog' in class com.atlassian.jira.util.JiraVelocityHelper threw exception com.atlassian.jira.issue.customfields.impl.FieldValidationException: Invalid priority name 'Enhancement'. at templates/email/macros.vm[line 40, column 74]
at org.apache.velocity.runtime.parser.node.ASTMethod.handleInvocationException(ASTMethod.java:337)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:284)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:262)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:342)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:212)
at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:247)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:175)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:336)
at org.apache.velocity.runtime.RuntimeInstance.render(RuntimeInstance.java:1277)
at org.apache.velocity.runtime.RuntimeInstance.evaluate(RuntimeInstance.java:1216)
at org.apache.velocity.runtime.RuntimeInstance.evaluate(RuntimeInstance.java:1165)
at org.apache.velocity.app.VelocityEngine.evaluate(VelocityEngine.java:219)
at com.atlassian.velocity.DefaultVelocityManager.writeEncodedBodyForContent(DefaultVelocityManager.java:86)
at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest.toWriterImpl(DefaultVelocityTemplatingEngine.java:157)
at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest.asPlainText(DefaultVelocityTemplatingEngine.java:128)
at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest$1.with(DefaultVelocityTemplatingEngine.java:108)
at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest$StringRepresentation.toString(DefaultVelocityTemplatingEngine.java:88)
at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest.asPlainText(DefaultVelocityTemplatingEngine.java:104)
at com.atlassian.jira.mail.builder.EmailRenderer.renderEmailBody(EmailRenderer.java:117)
at com.atlassian.jira.mail.builder.EmailRenderer.render(EmailRenderer.java:165)
at com.atlassian.jira.mail.builder.EmailBuilder.renderNow(EmailBuilder.java:162)
at com.atlassian.jira.mail.builder.EmailBuilder.renderNowAsQueueItem(EmailBuilder.java:152)
at com.atlassian.jira.mail.MailingListCompiler$1.processRecipient(MailingListCompiler.java:306)
at com.atlassian.jira.mail.NotificationRecipientProcessor.process(NotificationRecipientProcessor.java:39)
at com.atlassian.jira.mail.MailingListCompiler.addMailsToQueue(MailingListCompiler.java:331)
at com.atlassian.jira.mail.MailingListCompiler.access$200(MailingListCompiler.java:46)
at com.atlassian.jira.mail.MailingListCompiler$NotificationCompiler.addEmailsToQueue(MailingListCompiler.java:454)
at com.atlassian.jira.mail.MailingListCompiler$NotificationCompiler.sendLists(MailingListCompiler.java:424)
at com.atlassian.jira.mail.MailingListCompiler$NotificationCompiler.sendNoLevelsIgnoreGroup(MailingListCompiler.java:404)
at com.atlassian.jira.mail.MailingListCompiler$NotificationCompiler.sendToAll(MailingListCompiler.java:399)
at com.atlassian.jira.mail.MailingListCompiler.sendLists(MailingListCompiler.java:144)
at com.atlassian.jira.mail.IssueMailQueueItem.send(IssueMailQueueItem.java:149)
at com.atlassian.mail.queue.MailQueueImpl.sendBuffer(MailQueueImpl.java:66)
at com.atlassian.jira.service.services.mail.MailQueueService.run(MailQueueService.java:28)
at com.atlassian.jira.service.JiraServiceContainerImpl.run(JiraServiceContainerImpl.java:61)
at com.atlassian.jira.service.ServiceRunner.execute(ServiceRunner.java:48)
at org.quartz.core.JobRunShell.run(JobRunShell.java:195)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)
Caused by: com.atlassian.jira.issue.customfields.impl.FieldValidationException: Invalid priority name 'Enhancement'.
at com.atlassian.jira.issue.fields.PrioritySystemField.getPriorityTypeIdByName(PrioritySystemField.java:176)
at com.atlassian.jira.issue.fields.PrioritySystemField.prettyPrintChangeHistory(PrioritySystemField.java:375)
at com.atlassian.jira.util.JiraVelocityHelper.getPrettyFieldString(JiraVelocityHelper.java:275)
at com.atlassian.jira.util.JiraVelocityHelper.printChangelog(JiraVelocityHelper.java:184)
at sun.reflect.GeneratedMethodAccessor2050.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:381)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:370)
at com.atlassian.velocity.htmlsafe.introspection.UnboxingMethod.invoke(UnboxingMethod.java:30)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:270)
... 39 more