Crashes on PgDown #82
Description
The application crashes when I press the PageDown button:
$ ctop -v
ctop version 0.6.0, build 617b1b2
goroutine 239 [running]:
github.com/bcicen/ctop/cwidgets/compact.(*CompactGrid).Align(0xc4201b2e10)
/home/bradley/go/src/github.com/bcicen/ctop/cwidgets/compact/grid.go:29 +0x28e
main.(*GridCursor).PgDown(0xc4201a4e40)
/home/bradley/go/src/github.com/bcicen/ctop/cursor.go:180 +0x1c4
main.(*GridCursor).PgDown-fm()
/home/bradley/go/src/github.com/bcicen/ctop/grid.go:88 +0x2a
main.HandleKeys.func1(0x95ce4d, 0x8, 0xc420298010, 0xf, 0x95c723, 0x7, 0x0, 0x0, 0x8d4720, 0xc420298020, ...)
/home/bradley/go/src/github.com/bcicen/ctop/keys.go:39 +0x24
github.com/bcicen/ctop/vendor/github.com/gizak/termui.(*EvtStream).Loop.func1(0xc42001c730, 0x95ce4d, 0x8, 0xc420298010, 0xf, 0x95c723, 0x7, 0x0, 0x0, 0x8d4720, ...)
/home/bradley/go/src/github.com/bcicen/ctop/vendor/github.com/gizak/termui/events.go:251 +0xff
created by github.com/bcicen/ctop/vendor/github.com/gizak/termui.(*EvtStream).Loop
/home/bradley/go/src/github.com/bcicen/ctop/vendor/github.com/gizak/termui/events.go:253 +0x167