fixed null pointer exception during undo for rollback

git-svn-id: https://hyracks.googlecode.com/svn/branches/hyracks_lsm_tree@2495 123451ca-8445-de46-9d55-352943316053
diff --git a/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTreeOpContext.java b/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTreeOpContext.java
index 04997b5..852bc2b 100644
--- a/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTreeOpContext.java
+++ b/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTreeOpContext.java
@@ -88,6 +88,7 @@
                 setInsertMode();
                 break;
 
+            case PHYSICALDELETE:
             case DELETE:
                 setDeleteMode();
                 break;