Proper partial display for LineChart
Proper partial display for LineChart

If some of the visible data entries in a line chart were nil, the
LineChartRenderer used to draw non of them.

Now the LineChartRenderer renders everything from the first visible
non-nil entry until the last visible entry or the next nil-entry.

leoMehlig/Charts,leoMehlig/ios-charts,leoMehlig/Charts,leoMehlig/ios-charts,leoMehlig/Charts,leoMehlig/Charts,leoMehlig/ios-charts,leoMehlig/ios-charts