Task is not assigned to next user if document is not uploaded
I have document upload field in form. If i upload document it is forward to next user if it is not uploaded the it is not assigned to next user. I need that if document is uploaded or not it must be forward to next user. how can i make it possible in Bonita BPM Community Edition Version : 7.3.1. I also want to know that how can i access document variable in script defined in document tab.