Fatal error: Cannot unset string offsets in JqplotDataGenerator

[tsteur]

Following error happened on index.php?date=2018-03-18&viewDataTable=graphVerticalBar&module=VisitTime&action=getByDayOfWeek&widget=1&columns_to_display=nb_actions%2Cnb_uniq_visitors&idSite=1&period=week

"message":"Cannot unset string offsets","file":"plugins\/CoreVisualizations\/JqplotDataGenerator.php","line":106

Haven't tried to reproduce myself so not sure if it is an easy fix or not.

[sgiehl]

Can be easily reproduces on demo: https://demo.matomo.org/index.php?date=2018-03-18&viewDataTable=graphVerticalBar&module=VisitTime&action=getByDayOfWeek&widget=1&columns_to_display=nb_actions,nb_uniq_visitors&idSite=7&period=week

But that might be by design. columns_to_display is handled as array, but a string is given in URL. Correct would be columns_to_display[]=nb_actions&columns_to_display[]=nb_uniq_visitors

Need to investigate if we generate such broken urls anywhere in the code...

[mattab]

(It is also reproduced several times by customers)

[sgiehl]

Do you know a way to reproduce it in Matomo without calling the API directly (with incorrect params)