terminal window appears every boot - why?

Using SolydXK - a debian derivative on a DELL 1525 latptop.
Xfce is the desktop manager.

I decided to try to shut down the computer from the terminal,
so I wrote a script that calls xfce4-session-logout --halt.
It worked well.

But now, every time I start the computer, a blank terminal window
comes up on the desktop. This happens even if I shut the computer
down last time using the xfce4-session-logout dialog...

How can I get rid of it?

Thanks..

Phil