Fixed the invalid duplicate left over nodes.

* Accidently introduced that bug in r43837; the arrayCount variable was not
  being updated after the value got removed.

src/add-ons/kernel/file_systems/bfs/BPlusTree.cpp

@@ -1812,8 +1812,10 @@ BPlusTree::_RemoveDuplicate(Transaction& transaction,
 			return B_BAD_DATA;
 		}
 
-		if (array->Remove(value))
+		if (array->Remove(value)) {
+			arrayCount--;
 			break;
+		}
 
 		if ((duplicateOffset = duplicate->RightLink()) == BPLUSTREE_NULL)
 			RETURN_ERROR(B_ENTRY_NOT_FOUND);