NULL pointer Exception in Groovy postbuild Script - jenkins

Question

I am using the build flow project for combining the two different project test results.Then i am in need to change the build status of the aggregated test results so i am using groovy postbuild to change my build status.In that script if any one of the test fails gets failed in any of the projects then i am trying to change the build status to unstable.For that i am calculating the fail counts from both results using groovy script.But when i am trying this it throws the NULL pointer Exception.
The script i used in the groovy postbuild is
def testResult = manager.build.testResultAction.result
def fail = testResult.failCount
if(fail==NULL)
{ manager.buildSuccess() }
else
{ manager.buildUnstable() }
It throws the exception as
ava.lang.NullPointerException: Cannot get property 'result' on null object
at org.codehaus.groovy.runtime.NullObject.getProperty(NullObject.java:56)
at org.codehaus.groovy.runtime.InvokerHelper.getProperty(InvokerHelper.java:156)
at org.codehaus.groovy.runtime.callsite.NullCallSite.getProperty(NullCallSite.java:44)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:227)
at Script1.run(Script1.groovy:1)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:580)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:618)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:589)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:166)
at org.jvnet.hudson.plugins.groovypostbuild.GroovyPostbuildRecorder.perform(GroovyPostbuildRecorder.java:362)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:782)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:723)
at hudson.model.Build$BuildExecution.post2(Build.java:185)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:668)
at hudson.model.Run.execute(Run.java:1763)
at hudson.model.FreeStyleBuild.run``(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)
Activity