[AGIPD] [PC] Fixing ValueError

Description

Fixes an error in condition checking whether any old constants were retrieved.

How Has This Been Tested?

/gpfs/exfel/exp/SPB/202331/p900376/scratch/PC_test/12on/ runs 313-320 12on_900376_r313_r320.pdf

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

Reviewers

@ahmedk @jsztuk

added Waiting for review label

requested review from @ahmedk

assigned to @rovensky

changed the description

marked this merge request as ready

changed the description

LGTM.

It would be good to change the retrieving part to the new CALCAT API when we start integrating it into the other notebook. But don't mind this now.

Thanks for checking! Sure, we can discuss this.

merged

mentioned in commit 0831b69c

changed milestone to %3.13.0