Hello I am facing a issue regarding my mern project

I’ve created a bolg api with inputs of title,paragraph, and image… for storing images to server I have used multer package. At the time of post request on api I have no issue, but while I am trying to update same blog id api I need to select image file and send it to api else multer won’t work with error “cannot read property ‘filename’ of undefined”, I just what to make either user can update any one of blog details and rest other details can be same, how can I bypass multer field if user don’t want to update new image. please help me!!!