editor: holding up/down in game sometimes seems to scroll the code view

[increpare]

chrome/windows - doesn't always happen - not sure what the exact repro is

should probably more aggressively grab focus from codemirror when getting input.

[david-pfx]

It's not that. It happens when a key of a kind that is used by the game engine is actually not used, such as a duplicate or some kind of if statement. Then the event can bubble to the editor.

I fixed this in PS Next by adding prevent(event) to catch all of those code paths.