add getAbove() in Matchfield - Case: nothingAbove

src/main/java/de/tims/fleetstorm/matchfield/Matchfield.java

@@ -56,7 +56,9 @@ public class Matchfield {
 	}
 
 	public Coordinate getAbove(Coordinate center) {
-
+		if (center.getY() == matchfield.length - 1) {
+			return null;
+		}
 		return matchfield[center.getX()][center.getY() + 1];
 	}
 

src/test/java/de/tims/fleetstorm/matchfield/MatchfieldCreationTest.java

@@ -106,7 +106,9 @@ class MatchfieldCreationTest {
 
 	static Stream<Arguments> getCoordinateAbove() {
 		Matchfield matchfield = new Matchfield(10);
-		return Stream.of(Arguments.of("above from (5/5) - should be (5,6)", matchfield, new Coordinate(5, 5),
-				matchfield.getField(5, 6)));
+		return Stream.of(
+				Arguments.of("above from (5/5) - should be (5,6)", matchfield, new Coordinate(5, 5),
+						matchfield.getField(5, 6)),
+				Arguments.of("above from (5/9) - should be null", matchfield, new Coordinate(5, 5), null));
 	}
 }