Unexpected time series fill result on a merged time series

[katrotz]

When executing the fill operation on a timeSeries that is the result of the TimeSeries.timeSeriesListMerge, the fill seems not to work.

// Input time series 1
var ts1 = new TimeSeries({
        name: 'telemetry',
	columns: [ 'time', 'pressure' ],
        points: [
             [ 1530226800000, 1 ] 
        ]
});
// Input time series 2
var ts2 = new TimeSeries({
	name: 'telemetry',
	columns: [ 'time', 'temperature' ],
        points: [
            [ 1530226800000, 10], 
            [ 1530226800001, 11 ]
        ]
});
// Time series that combines ts1 and ts2 MANUALLY created
var tsCombined = new TimeSeries({
	name: 'telemetry',
	columns: [ 'time', 'pressure',  'temperature' ],
        points: [
    	    [ 1530226800000, 1, 10 ],
    	    [ 1530226800001, undefined, 11 ]
        ]
});
// Time series that combines ts1 and ts2 MERGE created
var tsMerge = TimeSeries.timeSeriesListMerge({
	name: 'telemetry',
	seriesList: [ ts1, ts2 ]
});
// Fill the combines MANUAL time series
var tsCombinedFill = tsCombined.fill({
	fieldSpec: [ 'pressure', 'temperature' ],
	method: 'pad'
});
// Fill the combined MERGE time series
var tsMergeFill = tsMerge.fill({
	fieldSpec: [ 'pressure', 'temperature' ],
	method: 'pad'
});

Expecting that the merged time series to render same results as the manually combines time series
Actually it is not filling the gaps:

tsCombinedFill.toString()
// "{"name":"telemetry","utc":true,"columns":["time","pressure","temperature"],"points":[[1530226800000,1,10],[1530226800001,1,11]]}"
tsMergeFill.toString()
// "{"name":"telemetry","utc":true,"columns":["time","pressure","temperature"],"points":[[1530226800000,1,10],[1530226800001,null,11]]}"

[katrotz]

Please note that creating a new time series from a merged time series will correctly fill the gaps:

(new TimeSeries(tsMerge.toJSON())).fill({
	fieldSpec: [ 'pressure', 'temperature' ],
	method: 'pad'
})