Fix issue when IslandTypeChallenges required blocks were cleared if c…

…ompletion was uncessesfull.

The issue was that it cleared wrong map. It must clear priority queue, but cleared required elements.

src/main/java/world/bentobox/challenges/tasks/TryToComplete.java

@@ -162,7 +162,9 @@ public TryToComplete(ChallengesAddon addon,
         this.permissionPrefix = permissionPrefix;
         this.user = user;
         this.manager = addon.getChallengesManager();
-        this.challenge = challenge;
+        // To avoid any modifications that may accure to challenges in current completion
+        // just clone it.
+        this.challenge = challenge.clone();
         this.topLabel = topLabel;
     }
 
@@ -1021,7 +1023,7 @@ private ChallengeResult searchForBlocks(Map<Material, Integer> requiredMap, int
         // kick garbage collector
         blocks.clear();
         blocksFound.clear();
-        requiredMap.clear();
+        blockFromWorld.clear();
 
         return EMPTY_RESULT;
     }