A FILE object defined in the contract is always madatory? Bonita 7.0.2

I am testing this process to upload and download files. I have set the mandatory property of upload widget to false.
When I throw the process, if I do not select a file in "Step Upload" and click "submit" the process does not continue to the next task and this message catalina log:

BONITA 7: Start a process instance from script

Hello, In Bonita 7 I'm trying to create a new instance of a process from a script but I can not. My process (process1) has a service task in which I add a script to launch a new process called "process2" version "1.0". Examples of Bonita's documentation not have all the code and sometimes lack me how to get the current session, other times to get the current users ... please does anyone have a complete example or can help me?

Thank you. Regards,

How to use CSS in BONITA 7? How to modify the height of a text widget or input widget?

Please, I need to modify the height of a text widget.

How to create a class in CSS and use it in UI Designer? This example doesn't work.