A few changes to the QML UI

[Dirk Hohndel]

> On Apr 14, 2018, at 9:27 PM, Miika Turkia <miika.turkia at gmail.com> wrote:
> 
> I have the same scrolling jerkyness as Linus on iPhone 5S. iPhone 8 is a lot better but as I know about the problem, I can see it there as well. Feels like the problem might be related to scrolling to next trip. Maybe processing all the dives within a trip?

We are simply making all the dives that we aren't showing (a) invisible and (b) have a height of 0.
I don't see how that would be MORE work than not doing that and actually having to render the dives.

/D