that this feature is now deprecated.

Non-functional change.

Ryan reported a dead lock caused by getView(String), so removing synchronized and requiring the list be concurrently iterable.

mavenExecutionResult exceptions not empty
message : Internal error: java.lang.NullPointerException
cause : null
Stack trace :
org.apache.maven.InternalErrorException: Internal error: java.lang.NullPointerException
	at org.apache.maven.lifecycle.internal.BuilderCommon.handleBuildError(BuilderCommon.java:128)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:95)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:319)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
	at org.jvnet.hudson.maven3.launcher.Maven3Launcher.main(Maven3Launcher.java:79)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchStandard(Launcher.java:329)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:239)
	at org.jvnet.hudson.maven3.agent.Maven3Main.launch(Maven3Main.java:158)
	at hudson.maven.Maven3Builder.call(Maven3Builder.java:121)
	at hudson.maven.Maven3Builder.call(Maven3Builder.java:73)
	at hudson.remoting.UserRequest.perform(UserRequest.java:118)
	at hudson.remoting.UserRequest.perform(UserRequest.java:48)
	at hudson.remoting.Request$2.run(Request.java:287)
	at java.util.concurrent.Executors$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$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
	at hudson.maven.MojoInfo.intercept(MojoInfo.java:208)
	at hudson.maven.reporters.MavenArtifactArchiver.preExecute(MavenArtifactArchiver.java:74)
	at hudson.maven.Maven3Builder$MavenExecutionListener.recordMojoStarted(Maven3Builder.java:535)
	at hudson.maven.Maven3Builder$MavenExecutionListener.forkStarted(Maven3Builder.java:671)
	at org.apache.maven.lifecycle.internal.DefaultExecutionEventCatapult.fire(DefaultExecutionEventCatapult.java:94)
	at org.apache.maven.lifecycle.internal.DefaultExecutionEventCatapult.fire(DefaultExecutionEventCatapult.java:42)
	at org.apache.maven.lifecycle.internal.MojoExecutor.executeForkedExecutions(MojoExecutor.java:328)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:199)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
	... 24 more
channel stopped
FATAL: null
java.lang.NullPointerException
	at hudson.maven.MavenModuleSetBuild$RunnerImpl.doRun(MavenModuleSetBuild.java:833)
	at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:448)
	at hudson.model.Run.run(Run.java:1376)
	at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:479)
	at hudson.model.ResourceController.execute(ResourceController.java:88)
	at hudson.model.Executor.run(Executor.java:230)

Follow up fix to JENKINS-10640. Better to fix this in the base class to keep other implementations working.

[FIXED JENKINS-10640] GlobalConfiguration requires config.jelly, dies if not found