We've recently upgraded Jenkins to 1.536 and noticed that upon saving configuration of email-ext plugin breaks down.
Old configuration contained two entries in configuredTriggers and now looks like:

<configuredTriggers>
<null/>
<null/>
</configuredTriggers>

This causes build to crash with:
java.lang.NullPointerException
at hudson.plugins.emailext.ExtendedEmailPublisher._perform(ExtendedEmailPublisher.java:243)
at hudson.plugins.emailext.ExtendedEmailPublisher.prebuild(ExtendedEmailPublisher.java:222)
at hudson.model.AbstractBuild$AbstractBuildExecution.preBuild(AbstractBuild.java:815)
at hudson.model.AbstractBuild$AbstractBuildExecution.preBuild(AbstractBuild.java:810)
at hudson.model.Build$BuildExecution.doRun(Build.java:142)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:562)
at hudson.model.Run.execute(Run.java:1665)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:230)

Triggers section in Advanced looks broken too.
Removing triggers may help but works not always. Removing whole Email-ext postbuild helps.

Any idea what changes caused this?