#...
if (arg2)
     super(arg1, nil)
else
     super(nil)
     #...

Argument 2 for @NotNull parameter of org/jetbrains/plugins/ruby/ruby/codeInsight/resolve/ResolveUtil.addVariants must not be null
java.lang.IllegalArgumentException: Argument 2 for @NotNull parameter of org/jetbrains/plugins/ruby/ruby/codeInsight/resolve/ResolveUtil.addVariants must not be null
	at org.jetbrains.plugins.ruby.ruby.codeInsight.resolve.ResolveUtil.addVariants(ResolveUtil.java)
	at org.jetbrains.plugins.ruby.ruby.inspections.ducktype.MethodCallInspectionVisitorBase.resolveAndProcessCall(MethodCallInspectionVisitorBase.java:64)
	at org.jetbrains.plugins.ruby.ruby.inspections.ducktype.MethodCallInspectionVisitorBase.visitRCall(MethodCallInspectionVisitorBase.java:36)
	at org.jetbrains.plugins.ruby.ruby.lang.psi.impl.methodCall.RCallImpl.accept(RCallImpl.java:72)
	at com.intellij.codeInsight.daemon.impl.LocalInspectionsPass$1$1.run(LocalInspectionsPass.java:8)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:60)
	at com.intellij.codeInsight.daemon.impl.LocalInspectionsPass$1.process(LocalInspectionsPass.java:2)
	at com.intellij.codeInsight.daemon.impl.LocalInspectionsPass$1.process(LocalInspectionsPass.java:1)
	at com.intellij.concurrency.JobUtil$1.run(JobUtil.java:44)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269)
	at java.util.concurrent.FutureTask.run(FutureTask.java:123)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
	at java.lang.Thread.run(Thread.java:613)