[Solved]-Stepped line with null values in chart.js-Chart.js

This might not be exactly what you want but you can just add another point at 2012 with the same value as 2011 and then another data point at 2012 will null so it'll create a gap between 2012 and 2013, although it will create a point at 2012.

JSFiddle

_this.lines.labels = [2010,2011,2012,2012,2013,2014];
_this.lines.data = [
    [10, 5,5,null, 10, 5]    
];

This would be the only change to your current code