title: NullReferenceException: "Object reference not set to an instance of an object" when user clicks a button
body: <p>I have deployed my software to a few users around the world, and today one of them told me he got this error. I've never seen it when running the software on my own machine, and I've not gotten any other reports of it.</p>
  <p>When the user clicks a standard button, he gets the following error text:</p>
  <blockquote>
  <p>System.NullReferenceException: Object reference not set to an instance of an object.<br />
  at x.MainForm.btnCreateOutput_Click(Object sender, EventArgs e)<br />
  at System.Windows.Forms.Control.OnClick(EventArgs e)<br />
  at System.Windows.Forms.Button.OnClick(EventArgs e)<br />
  at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)<br />
  at System.Windows.Forms.Control.WmMouseUp(Message&amp; m, MouseButtons button, Int32 clicks)<br />
  at System.Windows.Forms.Control.WndProc(Message&amp; m)<br />
  at System.Windows.Forms.ButtonBase.WndProc(Message&amp; m)<br />
  at System.Windows.Forms.Button.WndProc(Message&amp; m)<br />
  at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp; m)<br />
  at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp; m)<br />
  at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)</p>
  </blockquote>
  <p>I'm not really sure what to make of this message.</p>
  <p>In <code>btnCreateOutput_Click</code> I just do some string work, I don't use the parameters of the function for anything.</p>
  <p>There are a lot of similar functions in the software, and the error only happens with this button apparently.</p>