Matomo reports "GitCommit" as "NaN"

This is happening in the Qualified Signature App:

POST https://analytics.tugraz.at/matomo.php?ping=1&idsite=131&rec=1&r=295151&h=15&m=31&s=49
  &url=https://mw-frontend-dev.tugraz.at/apps/signature/de/qualified-pdf-upload&_id=&_idn=1
  &_refts=0&send_image=0&cookie=1&res=1920x1080&_cvar={"1":["GitCommit","NaN"]}&pf_net=76
  &pf_srv=19&pf_tfr=0&pf_dm2=945&pf_onl=0&pv_id=tvbBjp

The Parameter GitCommit is reported an NaN