Plugin shouldn't use NullPointerException for non-exceptional code flow

 at java.util.ArrayList.addAll(ArrayList.java:702)
  at org.apache.maven.plugins.enforcer.RequirePluginVersions.getReportingPlugins(RequirePluginVersions.java:1062)
  at org.apache.maven.plugins.enforcer.RequirePluginVersions.getAllPluginEntries(RequirePluginVersions.java:970)
  at org.apache.maven.plugins.enforcer.RequirePluginVersions.execute(RequirePluginVersions.java:237)
  at org.apache.maven.plugins.enforcer.EnforceMojo.execute(EnforceMojo.java:199)
  - locked <0x1eb6> (a org.apache.maven.plugins.enforcer.RequirePluginVersions)
  at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
  at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute(MojoExecutor.java:301)
  at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:211)
  at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:165)
  at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:157)
  at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:121)
  at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:210)
  at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:195)
  at java.util.concurrent.FutureTask.run(FutureTask.java:264)
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
  at java.util.concurrent.FutureTask.run(FutureTask.java:264)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
  at java.lang.Thread.run(Thread.java:829)