Mark variable as required, but not sure whether the default web application checks variable accesses.
I marked the variable as required, it did not seem to make any difference, but perhaps you are right, the default webapp may pay no heed to the required status of variables,
there is no required (yet) on the webapp if a variable is required. In this case an empty string is posted so the processengine gets a variable and is fine.
ah ok thanks for confirming that