Issue in case of warmstarting case

[AleBasso80]

Hello,
I think I bumped into a code bug that has effect when a warmstarting is run and in the previous results (json file) there is an unsuccessful configuration. In that case the the fields "loss" and "info" of the job.results variable are both set to None, but not job.results itself. However the None check is performed only on job.result (that is not None), therefore when the "loss" field is called an exception is raised. I added the None check on the "loss" field as well in a few spots and now everything seems to be fine.