修复数据网格删除最后一条数据保存后仍存在的问题

o2web/source/x_component_process_Xform/DatagridMobile.js

@@ -1153,7 +1153,7 @@ MWF.xApplication.process.Xform.DatagridMobile = new Class({
 
             this._setBusinessData(this.gridData);
 
-            return (this.gridData.data.length) ? this.gridData : null;
+            return (this.gridData.data.length) ? this.gridData : {data:[]};
         }else{
             return this._getBusinessData();
         }

o2web/source/x_component_process_Xform/DatagridPC.js

@@ -1003,7 +1003,7 @@ MWF.xApplication.process.Xform.DatagridPC = new Class({
 
             this._setBusinessData(this.gridData);
 
-            return (this.gridData.data.length) ? this.gridData : null;
+            return (this.gridData.data.length) ? this.gridData : {data:[]};
         }else{
             return this._getBusinessData();
         }