diff --git a/src/main/java/world/bentobox/challenges/ChallengesImportManager.java b/src/main/java/world/bentobox/challenges/ChallengesImportManager.java
index 36b5655..47e0fca 100644
--- a/src/main/java/world/bentobox/challenges/ChallengesImportManager.java
+++ b/src/main/java/world/bentobox/challenges/ChallengesImportManager.java
@@ -241,7 +241,9 @@ public class ChallengesImportManager
                     this.addon.logWarning("challenges.messages.defaults-file-overwrite");
                 }
 
-                defaultFile.delete();
+                if (!defaultFile.delete()) {
+                    this.addon.logError("Could not delete file: " + defaultFile.getAbsolutePath());
+                }
             }
             else
             {
diff --git a/src/main/java/world/bentobox/challenges/ChallengesManager.java b/src/main/java/world/bentobox/challenges/ChallengesManager.java
index ec717c6..6624dc5 100644
--- a/src/main/java/world/bentobox/challenges/ChallengesManager.java
+++ b/src/main/java/world/bentobox/challenges/ChallengesManager.java
@@ -262,7 +262,7 @@ public class ChallengesManager
      * @param silent - if true, no messages are sent to user
      * @return - true if imported
      */
-    public boolean loadChallenge(@NonNull Challenge challenge,
+    public boolean loadChallenge(@Nullable Challenge challenge,
             boolean overwrite,
             User user,
             boolean silent)
@@ -346,7 +346,7 @@ public class ChallengesManager
      * @param silent of type boolean that indicate if message to user must be sent.
      * @return boolean that indicate about load status.
      */
-    public boolean loadLevel(@NonNull ChallengeLevel level,
+    public boolean loadLevel(@Nullable ChallengeLevel level,
             boolean overwrite,
             User user,
             boolean silent)