After upgrading to Jenkins 1.580.3 (fails with 1.608 too), scheduling a new release by clicking "Perform Maven Release" then "Schedule Maven Release build" is failing. It opens an error page with this NPE:

javax.servlet.ServletException: java.lang.NullPointerException
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:796)
        ...
Caused by: java.lang.NullPointerException
	at org.jvnet.hudson.plugins.m2release.M2ReleaseAction.getString(M2ReleaseAction.java:318)
	at org.jvnet.hudson.plugins.m2release.M2ReleaseAction.doSubmit(M2ReleaseAction.java:223)

Seems that StaplerRequest.getParameterMap() behavior changed, as httpParam map is empty instead of containing HTTP request parameters. Method M2ReleaseAction.getString() is not protected again this and causes the NPE.