nullreferenceexception on.. bracket?

Question

@if (Model.LastOrder != null)
{
    <h3>Lorem ipsum:</h3>
}
else
{
    <h3>Lorem lorem!</h3>
} -> here occurs error

With this code, I get an error nullreferenceexception. Everything could be easy to resolve, but error occurs at... last bracket! Very strange.. and what is more - nothing special is in error info to help me.

Why I get this error?

Here is my controller action:

[Authorize]
public ActionResult Dashboard()
{
     XYZ toReturn = new XYZ { };
     return View(toReturn);
}