The Axis suggested in a few places wasn't handling properly the case when there is no data available. They now default to the same behavior as the other IAxisSuggester classes.
* [src/AdapterUtils.cs] AxisSuggester_StartStep, AxisSuggester_Auto and AxisSuggester_RowAuto were suggesting wrong axis if there were no data.
* [src/HistogramPlot.cs] SuggestXAxis: If there is no data, you can't use it to adjust the suggested axis.
Signed off by: anmar
