Fix a cornercase crash
Fix a cornercase crash

If gtk_text_layout_move_cursor_visually is called with a
count of 0, we were passing NULL to a free function that
can't handle it. Don't do that.

https://bugzilla.gnome.org/show_bug.cgi?id=750058

grubersjoe/adwaita,jadahl/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,davidgumberg/gtk,grubersjoe/adwaita,chergert/gtk,Adamovskiy/gtk,chergert/gtk,alexlarsson/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,jigpu/gtk,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,jigpu/gtk,davidgumberg/gtk,chergert/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,Adamovskiy/gtk,chergert/gtk,chergert/gtk,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,jigpu/gtk,Adamovskiy/gtk,chergert/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jadahl/gtk,grubersjoe/adwaita,jigpu/gtk,Adamovskiy/gtk,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,jigpu/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk