Dynatrace integration : "String index out of range: -1" ?

Hello,

I'm trying to send NeoLoad results to Dynatrace after I've followed the documentation, but there is an error in the DynatraceEvent action when I launch the test script:

"java.lang.StringIndexOutOfBoundsException: String index out of range: -1"

Code error: NL-DYNATRACE_EVENT_ACTION-02

Nothing is writen in Dynatrace an I have no further informations :/

Thank you.