check if calibrator is none instead of calibrator manager

[gianlucadetommaso]

Check whether the output_calibrator is None, not the output_calib_manager.

Pull request type

Please check the type of change your PR introduces:

• [ x] Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

We erroneously check whether the output_calib_manager is None, but this is never the case.

What is the new behavior?

Check whether output_calibrator is None.