jobs requirements are not taken into account

[Sylvain Pineau]

All non-matching requirements return a None value that is now missing in the mask to evaluate the job requirements.
This is a regression in checkbox since rev 917.

File to fix: plugins/resource_info.py

Fix:
            mask.append(bool(new_values))
            if new_values is not None:
                values.extend(new_values)