remove error checking in hash-based accessor (#1326)

Author: baltzell

common-tools/clas-utils/src/main/java/org/jlab/utils/groups/IndexedList.java

@@ -146,7 +146,6 @@ public T getItem(int... index) {
      * @return the item with the hash, null if not found
      */
     public T getItemByHash(long hash){
-        if (!this.collection.containsKey(hash)) return null;
         return this.collection.get(hash);
     }