使用带有C＃.Net的MySQL时如何摆脱“空路径无效”错误

I am developing an application, where I use an update records form,to update data of a particular employee.If I press update button without changing any data of that employee,than an error comes for the picturebox control that "Empty path is not valid",while already an image is present in database for that record.But when I click picturebox control and upload the same image again than no error is given.This is a serious bug in my program.Kindly help me to get rid of it.I am developing an application, where I use an