DATAES - 865 - Fix MappingElasticsearchConverter writing an Object property containing a Map.

Original PR: spring-projects#482

Author: Been24

src/main/java/org/springframework/data/elasticsearch/core/convert/MappingElasticsearchConverter.java

@@ -596,7 +596,7 @@ private Object writeMapValue(Map<String, Object> value, ElasticsearchPersistentP
 		Map<Object, Object> target = new LinkedHashMap<>();
 		Streamable<Entry<String, Object>> mapSource = Streamable.of(value.entrySet());
 
-		if (!typeHint.getActualType().getType().equals(Object.class)
+		if (typeHint.getActualType() != null && !typeHint.getActualType().getType().equals(Object.class)
 				&& isSimpleType(typeHint.getMapValueType().getType())) {
 			mapSource.forEach(it -> {