Error on adding dataset in Time Scale chart

[Charlie-Hua]

Thanks for this awesome library!

My version is 2.0.0-beta2.
I am adding datasets dynamically by config.data.datasets[1] = ... or config.data.datasets.push(... in a Time Scale chart but having this error when updating:

TypeError: Cannot read property '0' of undefined
    at Chart.Scale.extend.getLabelMoment (Chart.js:6365)
    at Chart.Scale.extend.getPixelForValue (Chart.js:6536)
    at Chart.controllers.line.Chart.DatasetController.extend.updateElement (Chart.js:4849)
    at null.<anonymous> (Chart.js:4777)
    at Object.helpers.each (Chart.js:155)
    at update (Chart.js:4776)
    at helpers.extend.reset (Chart.js:1796)
    at null.<anonymous> (Chart.js:1416)
    at Object.helpers.each (Chart.js:155)
    at buildOrUpdateControllers (Chart.js:1402)

It can be easily reproduced in /samples/timeScale/line-time-scale.html by clicking "Add Dataset"

My workaround is to create empty datasets in advance, however, this can only be done by modifying the data attribute instead of assigning the whole dataset.
i.e. this works without error: config.data.datasets[1].data = [...
but this doesn't: config.data.datasets[1] = {data: [...
and the error:

TypeError: Cannot read property 'diff' of undefined
    at Chart.Scale.extend.getPixelForValue (Chart.js:6537)
    at Chart.controllers.line.Chart.DatasetController.extend.updateElement (Chart.js:4849)
    at null.<anonymous> (Chart.js:4777)
    at Object.helpers.each (Chart.js:155)
    at update (Chart.js:4776)
    at helpers.extend.reset (Chart.js:1796)
    at null.<anonymous> (Chart.js:1416)
    at Object.helpers.each (Chart.js:155)
    at buildOrUpdateControllers (Chart.js:1402)
    at update (Chart.js:1442)

Thank you!

[etimberg]

@Charlie-Hua fixed in #1929

[Charlie-Hua]

wow that was fast!
I will try the next release. Big thanks!