When using stepPlot, if the graph have NaN values at the beginning or in the middle of the series, they are seen as gaps in the line, as they should. But if the NaN values are at the end of the series, they aren't seen as gap and the graph plots as if they were the same value that the precedent.
This only happens in stepPlotmode, in normal mode they are ignored, as the should.
You can see the behaviour here: https://jsfiddle.net/LostInBrittany/Lrqm0c91/2/
The problem exist in all browsers (seen in Chrome, FF and Edge, on Windows and linux), using Dygraphs 1.1.1