If - else statement without else

Could someone explain me why the if - else statement works like this and not throw an error or exeption? also if this is intentional in C# could someone explain if there is a diffrence between the 2?

if (comboBox1.SelectedIndex == -1) { }
    {
            //code
    }

rather then using

  if (comboBox1.SelectedIndex == -1) { }
  else {
            //code
       }

Since I noticed I accidentally made a if - else statement like the above one in my code after I re-arranged the code to make it more readable.