[7.0.5] Error trying to show or export to pdf S curve report - by: DF31

Each time i try to show or export to pdf S curve report th e result is on error and in th the log file i can see :

2018-04-24 13:45:07.694 ***** ERROR ***** [V7.0.5] ERROR *****
2018-04-24 13:45:07.695 ***** ERROR ***** [V7.0.5] on file '/volume1/web/Projeqtor/report/headerFunctions.php' at line (89)
2018-04-24 13:45:07.695 ***** ERROR ***** [V7.0.5] cause = dirname() expects exactly 1 parameter, 2 given

Thank you for your help