add: assert messages when create polygon

Author: wjdqhry

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonPolygon.java

@@ -126,6 +126,12 @@ public List<GeoJsonLineString> getCoordinates() {
 
 	private static List<Point> asList(Point first, Point second, Point third, Point fourth, Point... others) {
 
+		Assert.notNull(first, "First point must not be null");
+		Assert.notNull(second, "Second point must not be null");
+		Assert.notNull(third, "Third point must not be null");
+		Assert.notNull(fourth, "Fourth point must not be null");
+		Assert.notNull(others, "Additional points must not be null");
+
 		ArrayList<Point> result = new ArrayList<Point>(4 + others.length);
 
 		result.add(first);