Password parameter default value one enters seems not to be persisted, so jobs
which are triggered automatically or run manually without user setting password
parameter value, fail with the NPE exception (see [1]). When Hudson
(MavenBuilder) tries to set/put all system properties back to the system
including a null value I suppose for that password parameter, since system
properties are held in a Hashtable which doesn't support null values, we got a NPE.

[1] build job execution stack trace snippet

ERROR: Processing failed due to a bug in the code. Please report this to
users@hudson.dev.java.net
java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:394)
at java.util.Hashtable.putAll(Hashtable.java:466)
at hudson.maven.MavenBuilder.call(MavenBuilder.java:156)
at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:685)
at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:631)
at hudson.remoting.UserRequest.perform(UserRequest.java:103)
at hudson.remoting.UserRequest.perform(UserRequest.java:47)
at hudson.remoting.Request$2.run(Request.java:236)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)