Time series tooltip bug

It's a weird bug with a timeline tooltip when chart data is loaded dynamically:

http://jsfiddle.net/untit1ed/z1duqgt3/2/ - run the fiddle and mouse over the chart to show the tooltip.

My guess what's going on:
When there's a timeline chart with multiple data sets and some data sets have no value for a specific time then the tooltip stops working properly, it gets stuck on the right side, showing only one dataset value. If all x values are present in every dataset then it works fine - http://jsfiddle.net/untit1ed/xdaff593/

Updated the fiddle, so the bug is reproduced on every run.