-bind $ui_diff <Key-Up> {%W yview scroll -1 units}
-bind $ui_diff <Key-Down> {%W yview scroll 1 units}
-bind $ui_diff <Key-Left> {%W xview scroll -1 units}
-bind $ui_diff <Key-Right> {%W xview scroll 1 units}
+bind $ui_diff <Key-Up> {catch {%W yview scroll -1 units};break}
+bind $ui_diff <Key-Down> {catch {%W yview scroll 1 units};break}
+bind $ui_diff <Key-Left> {catch {%W xview scroll -1 units};break}
+bind $ui_diff <Key-Right> {catch {%W xview scroll 1 units};break}