title: Powermock Whitebox invocation with null parameter
body: <p>I'm trying to test a private method and have the following setup:</p>
  
  <pre>
  public class MyClass {
    private boolean myprivatemethod(ClassB classBObject, boolean b) {
      // do stuff here
      someOtherMethod();
    }
  
    private void someOtherMethod() {
      // more stuff
    }
  }
  
  final MyClass testsubject = PowerMockito.spy(new MyClass());
  // spy is needed because "someOtherMethod" is mocked 
  // which is not shown here for simplicity
  ClassB classBObject = mock(ClassB.class);
  
  boolean result = Whitebox.invokeMethod(testsubject, "myprivatemethod", classBObject, true);
  </pre>
  
  <p>This works nice until I try to run the method with <code>null</code> as the ClassB object:</p>
  
  <pre>
  boolean result = Whitebox.invokeMethod(testsubject, "myprivatemethod", null, true);
  </pre>
  
  <p>This results in the following exception:</p>
  
  <pre>
  java.lang.NullPointerException
      at java.lang.Class.isAssignableFrom(Native Method)
      at org.powermock.reflect.internal.WhiteboxImpl.checkIfParameterTypesAreSame(WhiteboxImpl.java:2432)
      at org.powermock.reflect.internal.WhiteboxImpl.getMethods(WhiteboxImpl.java:1934)
      at org.powermock.reflect.internal.WhiteboxImpl.getBestMethodCandidate(WhiteboxImpl.java:1025)
      at org.powermock.reflect.internal.WhiteboxImpl.findMethodOrThrowException(WhiteboxImpl.java:948)
      at org.powermock.reflect.internal.WhiteboxImpl.doInvokeMethod(WhiteboxImpl.java:882)
      at org.powermock.reflect.internal.WhiteboxImpl.invokeMethod(WhiteboxImpl.java:713)
      at org.powermock.reflect.Whitebox.invokeMethod(Whitebox.java:401)
      at test.myproject.TestMyClass.testMyClass(TestMyClass.java:10)
      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 junit.framework.TestCase.runTest(TestCase.java:154)
      at junit.framework.TestCase.runBare(TestCase.java:127)
      at junit.framework.TestResult$1.protect(TestResult.java:106)
      at junit.framework.TestResult.runProtected(TestResult.java:124)
      at junit.framework.TestResult.run(TestResult.java:109)
      at junit.framework.TestCase.run(TestCase.java:118)
      at junit.framework.TestSuite.runTest(TestSuite.java:208)
      at junit.framework.TestSuite.run(TestSuite.java:203)
      at org.powermock.modules.junit3.internal.impl.PowerMockJUnit3RunnerDelegateImpl.run(PowerMockJUnit3RunnerDelegateImpl.java:113)
      at org.powermock.modules.junit3.internal.impl.JUnit3TestSuiteChunkerImpl.run(JUnit3TestSuiteChunkerImpl.java:165)
      at org.powermock.modules.junit3.PowerMockSuite.run(PowerMockSuite.java:51)
      at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  </pre>
  
  <p>I'm using Powermockito 1.5.
  Is there any way to execute the method with <code>null</code> as parameter?</p>