allow empty array in createAll method

Author: Ajay Prajapati

lib/dao.js

@@ -512,11 +512,18 @@ DataAccessObject.createAll = function(dataArray, options, cb) {
   options = options || {};
   cb = cb || utils.createPromiseCallback();
 
-  assert(typeof dataArray === 'object' && dataArray.length,
-    'The data argument must be an array with length > 0');
+  assert(typeof dataArray === 'object' && Array.isArray(dataArray),
+  'The data argument must be an array');
   assert(typeof options === 'object', 'The options argument must be an object');
   assert(typeof cb === 'function', 'The cb argument must be a function');
 
+  if (dataArray.length === 0) {
+    process.nextTick(function() {
+     cb(null, []);
+    });
+    return cb.promise;
+  }
+
   const validationPromises = [];
   for (let index = 0; index < dataArray.length; index++) {
     const data = dataArray[index];