Cannot read property 'getTime' of null on monthly graph

[danielepercivaldi]

Hi.
When you go to monthly graph tab a red label appears and reads "Cannot read property 'getTime' of null". Only a yellow bar appears in the graph that is about the total of the first month.

Thanks for your support.

[kuzminets]

I had the same issue with the Daily Graph just after install vnstat, but it's gone on the next day. It looks the label is shown if there's only one item to display on a graph.