add getAbove() in Matchfield - Case: nothingAbove

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

@@ -41,6 +41,9 @@ public class Matchfield {
 	}
 
 	public Coordinate getField(int x, int y) {
+		if (x == 0) {
+			return null;
+		}
 		return matchfield[x][y];
 	}
 

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

@@ -74,6 +74,9 @@ class MatchfieldCreationTest {
 
 	static Stream<Arguments> getCoordinateAbove() {
 		Matchfield matchfield = new Matchfield(10);
-		return Stream.of(Arguments.of("above from (5/5)", matchfield, new Coordinate(5, 5), matchfield.getField(6, 5)));
+		return Stream.of(
+				Arguments.of("above from (5/5) - should be (6,5)", matchfield, new Coordinate(5, 5),
+						matchfield.getField(6, 5)),
+				Arguments.of("above from (0/5) - should be null", matchfield, new Coordinate(0, 5), null));
 	}
 }