Bug in gantt._init_tasks_range function

Hi all,
there is bug in method gantt._init_tasks_range. When tehere is not specified start_time and end_time and step on scale is not 1 then this method calculates min_date and max_date as follow:

this._min_date = this.calculateEndDate(this.date[unit + "_start"](this._min_date), -1, unit);//one free column before first task this._max_date = this.calculateEndDate(this._max_date, 2, unit);//one free column after last task

which is not good because its ignoring scale (or subscale) step. There should be new method:

gantt._scale_range_step = function(){ var step = this.config.step; if(this.config.scale_offset_minimal){ var scales = this._get_scales(); step = scales[scales.length - 1].step; } return step; };

and calculations made as follow:

this._min_date = this.calculateEndDate(this.date[unit + "_start"](this._min_date), -1 * this._scale_range_step(), unit);//one free column before first task this._max_date = this.calculateEndDate(this._max_date, 2 * this._scale_range_step(), unit);//one free column after last task

Best regards,
MM