Make sure truncate doesnt try to return affected rows for MSSQL

lib/dialects/mssql/query.js

@@ -149,7 +149,7 @@ module.exports = (function() {
     } else if (this.isBulkUpdateQuery()) {
       result = data.length;
     } else if (this.isBulkDeleteQuery()){
-      result = data[0].AFFECTEDROWS;
+      result = data[0] && data[0].AFFECTEDROWS;
     } else if (this.isVersionQuery()) {
       result = data[0].version;
     }