Fixed swap drag'n'drop mode (Fixed #137)

PlayWallCore/src/main/java/de/tobias/playpad/project/Project.java

@@ -108,6 +108,7 @@ public class Project {
 				}
 			}
 		}
+
 		Page page = pages.get(index.getPagePosition());
 		page.setPad(index.getId(), pad);
 	}

PlayWallCore/src/main/java/de/tobias/playpad/project/page/Page.java

@@ -205,9 +205,8 @@ public class Page implements Cloneable {
 	 * @param pad pad
 	 */
 	public void setPad(int id, Pad pad) {
-		if (pad == null) {
 		pads.removeIf(p -> p.getPosition() == id);
-		} else {
+		if (pad != null) {
 			pads.add(pad);
 			pad.setPage(this);
 			pad.setPosition(id);