Remove icon automatically by dropped file on RichTextBox

I set to true the AllowDrop implemented the DragOver and DragDrop events RichTextBox. On DragDrop event I load the dropped text files' contents on the RTB but it does add the icon of the file in RTB I'd to remove it:

Edit: Here's my code:

void msg_setup_dragDrop()
        {
            msg_textBox.AllowDrop = true;

msg_textBox.EnableAutoDragDrop = true; msg_textBox.DragEnter += new DragEventHandler(msg_DragEnter); msg_textBox.DragDrop += new DragEventHandler(msg_DragDrop); }

        void msg_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop))
                e.Effect = DragDropEffects.Copy;
        }

        void msg_DragDrop(object sender, DragEventArgs e)
        {
            string[] files = (string[]) e.Data.GetData(DataFormats.FileDrop);
            StringBuilder buffer = new StringBuilder();

            foreach (string filename in files)
            {
                try
                {
                    string text = File.ReadAllText(filename);
                    buffer.Append(text);
                }
                catch (Exception ex)
                {
                    string errMsg = string.Format("cannot read the file\"{0}\" error: {1}", filename, ex.Message);
                    MessageBox.Show(errMsg, "Reading file error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
            }

            msg_textBox.Text = buffer.ToString();
        }