Gridview not selecting Images gives error

I have a gridview where I have to select images via FileUpload and submit the button click so the path and related information gets submitted into the database.

But When I keep the gridview empty and click on submit button I get error as

Must declare the scalar variable "@img_path".

Is there any way by which I can provide validations so that user has to select the images and then only submit the form

Here is my code below:-

 protected void btnSubmit_Click(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DefaultCSRConnection"].ConnectionString);
        foreach (GridViewRow row in ImagesGrid.Rows)
        {
            var title = row.FindControl("txtTitle") as TextBox;
            var description = row.FindControl("txtDescription") as TextBox;
            var imageFile = row.FindControl("flUpload") as FileUpload;
            var chkDefault = row.FindControl("chkDefault") as CheckBox;
            using (SqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();
                SqlCommand cmd1 = new SqlCommand("Insert into tbl_galleries_stack (gallery_id,img_title,img_desc,img_path,IsDefault) values (@gallery_id,@img_title,@img_desc,@img_path,@IsDefault)", conn);
                cmd1.Parameters.Add("@gallery_id", SqlDbType.Int).Value = Convert.ToInt32(ddlgallery.SelectedValue);
                cmd1.Parameters.Add("@img_title", SqlDbType.NVarChar).Value = title.Text;
                cmd1.Parameters.Add("@img_desc", SqlDbType.NVarChar).Value = description.Text;
                if (imageFile.HasFile)
                {
                    imageFile.SaveAs(Server.MapPath("~/GalleryImages/") + imageFile.FileName);
                    cmd1.Parameters.Add("@img_path", SqlDbType.NVarChar).Value = "~/GalleryImages/" + imageFile.FileName;
                }
                cmd1.Parameters.Add("@IsDefault", SqlDbType.Bit).Value = chkDefault.Checked;
                cmd1.ExecuteNonQuery();
                conn.Close();
                ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('Gallery images added sucessfully');window.location ='csrgalleriesstack.aspx';", true);
            }
        }
    }

Please suggest what to do