fixed NPE if stdout isn't given:

Exception: 
Stacktrace:
java.lang.NullPointerException: out is null
	at hudson.util.StreamCopyThread.(StreamCopyThread.java:44)
	at hudson.util.StreamCopyThread.(StreamCopyThread.java:51)
	at hudson.Proc$LocalProc.(Proc.java:150)
	at hudson.Proc$LocalProc.(Proc.java:121)
	at hudson.Launcher$LocalLauncher.launch(Launcher.java:633)
	at hudson.Launcher$ProcStarter.start(Launcher.java:268)
	at hudson.Launcher$ProcStarter.join(Launcher.java:275)
	at hudson.plugins.script_realm.ScriptSecurityRealm.authenticate(ScriptSecurityRealm.java:62)
	at hudson.security.AbstractPasswordBasedSecurityRealm$Authenticator.retrieveUser(AbstractPasswordBasedSecurityRealm.java:137)
	at org.acegisecurity.providers.dao.AbstractUserDetailsAuthenticationProvider.authenticate(AbstractUserDetailsAuthenticationProvider.java:119)
	at org.acegisecurity.providers.ProviderManager.doAuthentication(ProviderManager.java:195)
	at org.acegisecurity.AbstractAuthenticationManager.authenticate(AbstractAuthenticationManager.java:45)
	at org.acegisecurity.ui.webapp.AuthenticationProcessingFilter.attemptAuthentication(AuthenticationProcessingFilter.java:71)
	at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:252)
	at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
	at org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
	at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
	at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
	at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
	at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
	at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
	at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
	at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
	at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
	at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
	at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
	at java.lang.Thread.run(Thread.java:637)


git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@29867 71c3de6d-444a-0410-be80-ed276b4c234a