e-canvas-background.c: Limit boundary rectangle to fit 'int' type
Running Evolution under Clang’s Ubsan prints:
../src/libgnomecanvas/gnome-canvas.c:3243:18: runtime error: signed integer overflow: 2147483647 - -2147483648 cannot be represented in type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../src/libgnomecanvas/gnome-canvas.c:3243:18 in
../src/libgnomecanvas/gnome-canvas.c:3244:19: runtime error: signed integer overflow: 2147483647 - -2147483648 cannot be represented in type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../src/libgnomecanvas/gnome-canvas.c:3244:19 in