Class Completion add a parameterless constructor.

Original Pull Request #2086
Closes #2085

Author: houtaroy

src/main/java/org/springframework/data/elasticsearch/core/suggest/Completion.java

@@ -28,13 +28,18 @@
  * @author Mewes Kochheim
  * @author Robert Gruendler
  * @author Peter-Josef Meisch
+ * @author Houtaroy
  */
 public class Completion {
 
 	private String[] input;
 	@Nullable private Map<String, List<String>> contexts;
 	@Nullable private Integer weight;
 
+	public Completion() {
+		this.input = new String[0];
+	}
+
 	@PersistenceConstructor
 	public Completion(String[] input) {
 		this.input = input;