Fix issue when ConfirmationGUI never closes.

src/main/java/world/bentobox/challenges/panel/admin/ListChallengesGUI.java

@@ -159,6 +159,8 @@ public class ListChallengesGUI extends CommonGUI
 					{
 						this.addon.getChallengesManager().deleteChallenge(challenge);
 					}
+
+					this.build();
 				});
 				return true;
 			});

src/main/java/world/bentobox/challenges/panel/admin/ListLevelsGUI.java

@@ -160,6 +160,8 @@ public class ListLevelsGUI extends CommonGUI
 						this.addon.getChallengesManager().
 							deleteChallengeLevel(challengeLevel);
 					}
+
+					this.build();
 				});
 				return true;
 			});