Fixes issue with null placeholder error

https://github.com/BentoBoxWorld/Level/issues/159

src/main/java/world/bentobox/level/Level.java

@@ -120,19 +120,27 @@ public class Level extends Addon {
 
     }
 
-    private String getRankName(World world, int rank) {
+    String getRankName(World world, int rank) {
         if (rank < 1) rank = 1;
         if (rank > 10) rank = 10;
         return getPlayers().getName(getManager().getTopTen(world, 10).keySet().stream().skip(rank - 1L).limit(1L).findFirst().orElse(null));
     }
 
-    private String getRankLevel(World world, int rank) {
+    String getRankLevel(World world, int rank) {
         if (rank < 1) rank = 1;
         if (rank > 10) rank = 10;
-        return getManager().formatLevel(getManager().getTopTen(world, 10).values().stream().skip(rank - 1L).limit(1L).findFirst().orElse(null));
+        return getManager()
+                .formatLevel(getManager()
+                        .getTopTen(world, 10)
+                        .values()
+                        .stream()
+                        .skip(rank - 1L)
+                        .limit(1L)
+                        .findFirst()
+                        .orElse(null));
     }
 
-    private String getVisitedIslandLevel(GameModeAddon gm, User user) {
+    String getVisitedIslandLevel(GameModeAddon gm, User user) {
         if (!gm.inWorld(user.getLocation())) return "";
         return getIslands().getIslandAt(user.getLocation())
                 .map(island -> getManager().getIslandLevelString(gm.getOverWorld(), island.getOwner()))

src/main/java/world/bentobox/level/LevelsManager.java

@@ -133,7 +133,8 @@ public class LevelsManager {
      * @param lvl - long value to represent
      * @return string of the level.
      */
-    public String formatLevel(long lvl) {
+    public String formatLevel(@Nullable Long lvl) {
+        if (lvl == null) return "";
         String level = String.valueOf(lvl);
         // Asking for the level of another player
         if(addon.getSettings().isShorthand()) {
@@ -270,7 +271,8 @@ public class LevelsManager {
      * @param size - size of the top ten
      * @return sorted top ten map
      */
-    public Map<UUID, Long> getTopTen(World world, int size) {
+    @NonNull
+    public Map<UUID, Long> getTopTen(@NonNull World world, int size) {
         topTenLists.computeIfAbsent(world, TopTenData::new);
         // Remove player from top ten if they are online and do not have the perm
         topTenLists.get(world).getTopTen().keySet().removeIf(u -> !hasTopTenPerm(world, u));
@@ -286,7 +288,7 @@ public class LevelsManager {
      * Checks if player has the correct top ten perm to have their level saved
      * @param world
      * @param targetPlayer
-     * @return
+     * @return true if player has the perm
      */
     boolean hasTopTenPerm(@NonNull World world, @NonNull UUID targetPlayer) {
         String permPrefix = addon.getPlugin().getIWM().getPermissionPrefix(world);

src/test/java/world/bentobox/level/LevelTest.java

@@ -300,5 +300,12 @@ public class LevelTest {
         assertEquals(100, s.getLevelCost());
     }
 
-
+    /**
+     * Test method for {@link world.bentobox.level.Level#getRankLevel(World, int)}.
+     */
+    @Test
+    public void testRankLevel() {
+        addon.onEnable();
+        assertEquals("",addon.getRankLevel(world, 1));
+    }
 }