Removed an unnessacary line of code in B-Tree

git-svn-id: https://java-algorithms-implementation.googlecode.com/svn/trunk@383 032fbc0f-8cab-eb90-e552-f08422b9a96a

Author: phishman3579

src/com/jwetherell/algorithms/data_structures/BTree.java

@@ -612,7 +612,6 @@ private T removeKey(int index) {
             if (index >= keysSize)
                 return null;
             T value = keys[index];
-            keys[index] = null;
             for (int i = index + 1; i < keysSize; i++) {
                 // shift the rest of the keys down
                 keys[i - 1] = keys[i];