private void modificarToolStripMenuItem_Click(object sender, EventArgs e)
{
if (modificar == null)
{
modificar = new ModificarTweet(negocio);
modificar.MdiParent = this;
modificar.Dock = DockStyle.Fill;
modificar.FormClosed += new FormClosedEventHandler(cerrarModicar);
modificar.Show();
}
else
{
modificar.Activate();
}
}