fixed hashmap constructor bug

src/main/java/Bins.java

@@ -2,9 +2,10 @@ import java.util.*;
 
 public class Bins {
 
-    HashMap<Integer, Integer> binResults = new HashMap<Integer, Integer>();
+    HashMap<Integer, Integer> binResults;
 
     Bins(int numOfDice){
+        binResults = new HashMap<Integer, Integer>();
         int size = getPossibleSize(numOfDice);
         for(int i = 0; i <= size; i++){
             binResults.put(i+numOfDice, 0);