Fixed label drawing bug
Fixed label drawing bug

For some reason the Y-Axis labels where disappearing when no data was
displayed in the LineChart.
This could happen, for example, if all currently visible data entries
where nil.

** I am not that familiar with all this CGContext stuff and find it vey
strange, that not calling a method in one renderer (LineChartRenderer)
has an affect on an other renderer (AxisYRenderer), but maybe someone
can explain and/or find a better solution then this one **

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