Remove useless test for @ValidateWith

You cannot pass `null` as a class literal: @ValidateWith(null) results
in a compiler error.

src/main/java/org/junit/validator/AnnotationValidatorFactory.java

@@ -27,9 +27,6 @@ public AnnotationValidator createAnnotationValidator(ValidateWith validateWithAn
  }
 
  Class<? extends AnnotationValidator> clazz = validateWithAnnotation.value();
- if (clazz == null) {
- throw new IllegalArgumentException("Can't create validator, value is null in annotation " + validateWithAnnotation.getClass().getName());
- }
  try {
  AnnotationValidator annotationValidator = clazz.newInstance();
  VALIDATORS_FOR_ANNOTATION_TYPES.putIfAbsent(validateWithAnnotation, annotationValidator);

src/test/java/org/junit/validator/AnnotationValidatorFactoryTest.java

@@ -1,14 +1,11 @@
 package org.junit.validator;
 
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.ExpectedException;
-
-import java.lang.annotation.Annotation;
-
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
 import static org.junit.Assert.assertThat;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 public class AnnotationValidatorFactoryTest {
 
@@ -22,26 +19,6 @@ public void createAnnotationValidator() {
  assertThat(annotationValidator, is(instanceOf(Validator.class)));
  }
 
- @Test
- public void exceptionWhenAnnotationWithNullClassIsPassedIn() {
- exception.expect(IllegalArgumentException.class);
- exception.expectMessage("Can't create validator, value is null in " +
- "annotation org.junit.validator.AnnotationValidatorFactoryTest$ValidatorWithNullValue");
-
- new AnnotationValidatorFactory().createAnnotationValidator(new ValidatorWithNullValue());
- }
-
-
- public static class ValidatorWithNullValue implements ValidateWith {
- public Class<? extends AnnotationValidator> value() {
- return null;
- }
-
- public Class<? extends Annotation> annotationType() {
- return ValidateWith.class;
- }
- }
-
  @ValidateWith(value = Validator.class)
  public static class SampleTestWithValidator {
  }