Bug#777082: (no subject)

[Michael Borkowski]

Despite the fact that I'm not running on Debian, I encountered this very
bug and indeed I can confirm that it seems to be related to multiple
screens.

However, I don't have to actually disable the secondary screen, it's
enough to move the mouse to the primary one, so that the window is
initially opend in the primary screen, which makes sweethome3d start up
nicely.