Handles null player world better on joining server

In theory, this should not be required, but it seems that a player's
world might be null in some edge cases. Alternatively, the Util.getWorld
function can return a null if the player was in a nether or end but that
does not have a corresponding overworld.
Addresses #2057

src/main/java/world/bentobox/bentobox/listeners/JoinLeaveListener.java

@@ -16,6 +16,7 @@ import org.bukkit.event.player.PlayerChangedWorldEvent;
 import org.bukkit.event.player.PlayerJoinEvent;
 import org.bukkit.event.player.PlayerQuitEvent;
 import org.eclipse.jdt.annotation.NonNull;
+import org.eclipse.jdt.annotation.Nullable;
 
 import world.bentobox.bentobox.BentoBox;
 import world.bentobox.bentobox.api.addons.GameModeAddon;
@@ -142,7 +143,7 @@ public class JoinLeaveListener implements Listener {
     }
 
     /**
-     * This event will clean players inventor
+     * This event will clean players inventory
      * @param event SwitchWorld event.
      */
     @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
@@ -161,8 +162,8 @@ public class JoinLeaveListener implements Listener {
      * @param world World where cleaning must occur.
      * @param user Targeted user.
      */
-    private void clearPlayersInventory(World world, @NonNull User user) {
+    private void clearPlayersInventory(@Nullable World world, @NonNull User user) {
-        if (user.getUniqueId() == null) return;
+        if (user.getUniqueId() == null || world == null) return;
         // Clear inventory if required
         Players playerData = players.getPlayer(user.getUniqueId());
 

src/test/java/world/bentobox/bentobox/listeners/JoinLeaveListenerTest.java

@@ -1,6 +1,7 @@
 package world.bentobox.bentobox.listeners;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
@@ -235,6 +236,29 @@ public class JoinLeaveListenerTest {
         verify(player, never()).sendMessage(anyString());
         // Verify resets
         verify(pm).setResets(eq(world), any(), eq(0));
+        // Verify inventory clear because of kick
+        // Check inventory cleared
+        verify(chest).clear();
+        verify(inv).clear();
+        assertTrue(set.isEmpty());
+        verify(pm, times(2)).save(any());
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.listeners.JoinLeaveListener#onPlayerJoin(org.bukkit.event.player.PlayerJoinEvent)}.
+     */
+    @Test
+    public void testOnPlayerJoinNullWorld() {
+        when(player.getWorld()).thenReturn(null); // Null
+        when(Util.getWorld(any())).thenReturn(null); // Make null
+        PlayerJoinEvent event = new PlayerJoinEvent(player, "");
+        jll.onPlayerJoin(event);
+        // Verify inventory clear because of kick
+        // Check inventory cleared
+        verify(chest, never()).clear();
+        verify(inv, never()).clear();
+        assertFalse(set.isEmpty());
+        verify(pm).save(any());
     }
 
     /**
@@ -334,13 +358,29 @@ public class JoinLeaveListenerTest {
     public void testOnPlayerSwitchWorld() {
         PlayerChangedWorldEvent event = new PlayerChangedWorldEvent(player, world);
         jll.onPlayerSwitchWorld(event);
-        // Player was kicked so check
+        // Check inventory cleared
         verify(chest).clear();
         verify(inv).clear();
         assertTrue(set.isEmpty());
         verify(pm).save(any());
     }
 
+    /**
+     * Test method for {@link world.bentobox.bentobox.listeners.JoinLeaveListener#onPlayerSwitchWorld(org.bukkit.event.player.PlayerChangedWorldEvent)}.
+     */
+    @Test
+    public void testOnPlayerSwitchWorldNullWorld() {
+        when(Util.getWorld(any())).thenReturn(null);
+        PlayerChangedWorldEvent event = new PlayerChangedWorldEvent(player, world);
+        jll.onPlayerSwitchWorld(event);
+        // These should not happen
+        verify(chest, never()).clear();
+        verify(inv, never()).clear();
+        assertFalse(set.isEmpty());
+        verify(pm, never()).save(any());
+    }
+
+
     /**
      * Test method for {@link world.bentobox.bentobox.listeners.JoinLeaveListener#onPlayerQuit(org.bukkit.event.player.PlayerQuitEvent)}.
      */