"t":null - error using jspsych eye tracking demo in cognition.run

[hadarMenahem]

I uploaded the External JS/CSS-fiels and I've used the code from the example on the 'Eye tracking' page on JsPsych website.
After running the experiment, I saw in the csv file of the data that "t":null under wegbgazer_data.
It is worth mentioning that "t":null also for webgazer-validate (that comes before wegbgazer_data ). The values for "x" and "y" are given but "t" is equal to null.
( "x":1041,"y":738,"t": null)
I would really appreciate if anyone could help me with this.