PageDown/PageUp only works once

Hello, maybe you can save me some time with this. Every time you press pageDown or up, the grid scrolls down by a set value,but if you try pressing it again this error comes up:

Uncaught TypeError: Cannot read property 'getCellOwnProperties' of undefined
at CellEvent.get (cellEventFactory.js:58)
at CellEvent.get (cellEventFactory.js:63)
at Constructor.handleKeyDown (CellSelection.js:103)
at Constructor.handleKeyDown (Filters.js:36)
at Constructor.onKeyDown (Behavior.js:917)
at Constructor.delegateKeyDown (events.js:581)
at events.js:458
at HTMLCanvasElement.decorator (events.js:32)
at Canvas.dispatchNewEvent (Canvas.js:313)
at Canvas.finkeydown (Canvas.js:453)
probably because theres no cell selected,therefore no origin position to scroll from
to test it out, just go on the demo and press pagedown a few times

Reproduce the issue in the demo by pressing PageDown or PageUp repeatedly and capture the second keypress failure. Start with cellEventFactory.js around line 58 and follow the key handling through CellSelection.js, Filters.js, and Behavior.js. Done means repeated PageUp/PageDown presses continue scrolling without the getCellOwnProperties error.

Written by the indexing model from the issue text.