Fix bug where drawing outline around accessible could result in a negative width or height.
Fix bug where drawing outline around accessible could result in
a negative width or height.

GNOME/orca,pvagner/orca,pvagner/orca,h4ck3rm1k3/orca-sonar,chrys87/orca-beep,pvagner/orca,chrys87/orca-beep,h4ck3rm1k3/orca-sonar,GNOME/orca,pvagner/orca,chrys87/orca-beep,GNOME/orca,GNOME/orca,chrys87/orca-beep,h4ck3rm1k3/orca-sonar