Added a failing test - but unsure how to proceed with the fix

Author: EdwardPrentice

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/MongoQueryCreator.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
+import static java.util.Objects.nonNull;
 import static org.springframework.data.mongodb.core.query.Criteria.*;
 
 import java.util.Arrays;
@@ -55,6 +56,7 @@
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Edward Prentice
  */
 class MongoQueryCreator extends AbstractQueryCreator<Query, Criteria> {
 
@@ -299,7 +301,8 @@ private Criteria createLikeRegexCriteriaOrThrow(Part part, MongoPersistentProper
 					criteria = criteria.not();
 				}
 
-				return addAppropriateLikeRegexTo(criteria, part, parameters.next().toString());
+				return addAppropriateLikeRegexTo(criteria, part, parameters.next() != null ? parameters.next().toString()
+						                                                           : null); // what to return? 
 
 			case NEVER:
 				// intentional no-op

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/AbstractPersonRepositoryIntegrationTests.java

@@ -67,6 +67,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Fırat KÜÇÜK
+ * @author Edward Prentice
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 public abstract class AbstractPersonRepositoryIntegrationTests {
@@ -654,6 +655,14 @@ public void executesGeoPageQueryForWithPageRequestForJustOneElementEmptyPage() {
 		assertThat(results.getAverageDistance().getMetric(), is((Metric) Metrics.KILOMETERS));
 	}
 
+	@Test // DATAMONGO-1608
+	public void findByFirstNameIgnoreCaseWithNull() {
+
+		List<Person> result = repository.findByFirstnameIgnoreCase(null);
+
+		assertThat(result.size(), is(nullValue()));
+	}
+
 	@Test // DATAMONGO-770
 	public void findByFirstNameIgnoreCase() {