Why does my form still add an item to the list when it is closed?

So far, I have a form1 where I press a button, it will load up a second form which has a couple of textboxes and a combobox to be filled in by the user which will then be added a to a list displayed in a listview on the form1. However, it works fine except when i close the second form either using a button or pressing the red X in the corner, it still adds a blank item to the list. Which is not really what I want it to do.

This is my code for the button on form1:

    private void button1_Click(object sender, EventArgs e)
    {
        // if there is less than items in the list, load the form
        if (addTask.Count < 10)
        {
            // New instance to load the form
            newTaskForm frm2 = new newTaskForm();
            frm2.ShowDialog();
            NewTask task = new NewTask();

                // Get the values entered by the user, eg title will be the text in textBox1 etc.
                task.title = frm2.textBox1.Text;
                task.description = frm2.textBox2.Text;
                try
                {
                    task.priority = frm2.comboBox1.SelectedItem.ToString();
                }
                catch
                {
                }
                task.completionDate = frm2.dateTimePicker1.Value.ToString();
                addTask.Add(task); // Add task to the list
                listView1.Items.Add(task.title); // Display task title in the list view

                // close form
                frm2.Close();
                frm2.Dispose();

            }            

        // if there are 10 items in the list, display a message
        else
        {
            MessageBox.Show("Maximum number of tasks added");
        }
    }

Then the code on my second form where the user enters the data is this.

  private void button1_Click(object sender, EventArgs e)
  {
      // check to see if all the fields have been filled in properly
      if (string.IsNullOrWhiteSpace(textBox1.Text) || string.IsNullOrWhiteSpace(textBox2.Text) || comboBox1.SelectedItem == null)
      {
          DialogResult = DialogResult.None; // do not send results back to main form
          MessageBox.Show("Please fill in all fields");
      }
      else
      {
          DialogResult = DialogResult.OK;
      }
  }

I just don't understand that when I press the Red X to close the second form, it adds a blank item to the list/listview?